diff --git a/lib/jsonapi_plug.ex b/lib/jsonapi_plug.ex
index 894fb47..2af8099 100644
--- a/lib/jsonapi_plug.ex
+++ b/lib/jsonapi_plug.ex
@@ -200,6 +200,16 @@ defmodule JSONAPIPlug do
       doc: "Controls wether the attribute is deserialized in requests.",
       type: :boolean,
       default: true
+    ],
+    required: [
+      doc: "Attribute is required.",
+      type: :boolean,
+      default: false
+    ],
+    type: [
+      doc: "Attribute type",
+      type: {:in, [:string, :number]},
+      default: :string
     ]
   ]
 
@@ -225,12 +235,8 @@ defmodule JSONAPIPlug do
               doc:
                 "Resource attributes. This will be used to (de)serialize requests/responses:\n\n" <>
                   NimbleOptions.docs(@attribute_schema, nest_level: 1),
-              type:
-                {:or,
-                 [
-                   {:list, :atom},
-                   {:keyword_list, [*: [type: [keyword_list: [keys: @attribute_schema]]]]}
-                 ]},
+              type: :keyword_list,
+              keys: [*: [type: :keyword_list, keys: @attribute_schema]],
               default: []
             ],
             id_attribute: [
diff --git a/lib/jsonapi_plug/document.ex b/lib/jsonapi_plug/document.ex
index 2139ff8..1df3afe 100644
--- a/lib/jsonapi_plug/document.ex
+++ b/lib/jsonapi_plug/document.ex
@@ -8,14 +8,9 @@ defmodule JSONAPIPlug.Document do
   https://jsonapi.org/format/#document-structure
   """
 
-  alias JSONAPIPlug.{
-    Document.ErrorObject,
-    Document.JSONAPIObject,
-    Document.LinkObject,
-    Document.ResourceObject,
-    Exceptions.InvalidDocument,
-    Resource
-  }
+  alias JSONAPIPlug.Document.{ErrorObject, JSONAPIObject, LinkObject, ResourceObject}
+  alias JSONAPIPlug.Exceptions.InvalidDocument
+  alias JSONAPIPlug.Resource
 
   @type value :: String.t() | integer() | float() | [value()] | %{String.t() => value()} | nil
 
@@ -99,7 +94,12 @@ defmodule JSONAPIPlug.Document do
   defp deserialize_data(%{"data" => _data, "errors" => _errors}) do
     raise InvalidDocument,
       message: "Document cannot contain both 'data' and 'errors' members",
-      reference: "https://jsonapi.org/format/#document-top-level"
+      errors: [
+        %ErrorObject{
+          title: "Document cannot contain both 'data' and 'errors' members",
+          detail: "https://jsonapi.org/format/#document-top-level"
+        }
+      ]
   end
 
   defp deserialize_data(%{"data" => resources}) when is_list(resources),
@@ -124,14 +124,24 @@ defmodule JSONAPIPlug.Document do
        when is_list(included) do
     raise InvalidDocument,
       message: "Document 'included' cannot be present if 'data' isn't also present",
-      reference: "https://jsonapi.org/format/#document-top-level"
+      errors: [
+        %ErrorObject{
+          title: "Document 'included' cannot be present if 'data' isn't also present",
+          detail: "https://jsonapi.org/format/#document-top-level"
+        }
+      ]
   end
 
   defp deserialize_included(%{"included" => included})
        when not is_nil(included) do
     raise InvalidDocument,
       message: "Document 'included' must be a list",
-      reference: "https://jsonapi.org/format/#document-top-level"
+      errors: [
+        %ErrorObject{
+          title: "Document 'included' must be a list",
+          detail: "https://jsonapi.org/format/#document-top-level"
+        }
+      ]
   end
 
   defp deserialize_included(_data), do: nil
@@ -152,7 +162,12 @@ defmodule JSONAPIPlug.Document do
   defp deserialize_meta(%{"meta" => meta}) when not is_nil(meta) do
     raise InvalidDocument,
       message: "Document 'meta' must be an object",
-      reference: "https://jsonapi.org/format/#document-meta"
+      errors: [
+        %ErrorObject{
+          title: "Document 'meta' must be an object",
+          detail: "https://jsonapi.org/format/#document-meta"
+        }
+      ]
   end
 
   defp deserialize_meta(_data), do: nil
@@ -183,11 +198,15 @@ defmodule JSONAPIPlug.Document do
 
   defp serialize_data(nil), do: nil
 
-  defp serialize_errors(errors)
-       when not is_nil(errors) and not is_list(errors) do
+  defp serialize_errors(errors) when not is_nil(errors) and not is_list(errors) do
     raise InvalidDocument,
       message: "Document 'errors' must be a list",
-      reference: "https://jsonapi.org/format/#document-top-level"
+      errors: [
+        %ErrorObject{
+          title: "Document 'errors' must be a list",
+          detail: "https://jsonapi.org/format/#document-top-level"
+        }
+      ]
   end
 
   defp serialize_errors(errors) when is_list(errors),
@@ -199,7 +218,12 @@ defmodule JSONAPIPlug.Document do
        when not is_nil(included) and not is_list(included) do
     raise InvalidDocument,
       message: "Document 'included' must be a list resource objects",
-      reference: "https://jsonapi.org/format/#document-top-level"
+      errors: [
+        %ErrorObject{
+          title: "Document 'included' must be a list resource objects",
+          detail: "https://jsonapi.org/format/#document-top-level"
+        }
+      ]
   end
 
   defp serialize_included(included) when is_list(included),
@@ -210,7 +234,12 @@ defmodule JSONAPIPlug.Document do
   defp serialize_meta(meta) when not is_nil(meta) and not is_map(meta) do
     raise InvalidDocument,
       message: "Document 'meta' must be a map",
-      reference: "https://jsonapi.org/format/#document-top-level"
+      errors: [
+        %ErrorObject{
+          title: "Document 'meta' must be a map",
+          detail: "https://jsonapi.org/format/#document-top-level"
+        }
+      ]
   end
 
   defp serialize_meta(meta), do: meta
diff --git a/lib/jsonapi_plug/document/jsonapi_object.ex b/lib/jsonapi_plug/document/jsonapi_object.ex
index fd78974..464522c 100644
--- a/lib/jsonapi_plug/document/jsonapi_object.ex
+++ b/lib/jsonapi_plug/document/jsonapi_object.ex
@@ -3,7 +3,9 @@ defmodule JSONAPIPlug.Document.JSONAPIObject do
   JSON:API Document JSON:API Object
   """
 
-  alias JSONAPIPlug.{Document, Exceptions.InvalidDocument}
+  alias JSONAPIPlug.Document
+  alias JSONAPIPlug.Document.ErrorObject
+  alias JSONAPIPlug.Exceptions.InvalidDocument
 
   @type version :: :"1.0" | :"1.1"
 
@@ -19,8 +21,14 @@ defmodule JSONAPIPlug.Document.JSONAPIObject do
 
   defp deserialize_meta(%{"meta" => _meta}) do
     raise InvalidDocument,
-      message: "JSON:API object 'meta' must be an object",
-      reference: "https://jsonapi.org/format/#document-jsonapi-object"
+      message: "JSON:API Object 'meta' must be an object",
+      errors: [
+        %ErrorObject{
+          title: "JSON:API object 'meta' must be an object",
+          detail: "https://jsonapi.org/format/#document-jsonapi-object",
+          source: %{pointer: "/jsonapi/meta"}
+        }
+      ]
   end
 
   defp deserialize_meta(_data), do: nil
@@ -30,7 +38,13 @@ defmodule JSONAPIPlug.Document.JSONAPIObject do
   defp deserialize_version(%{"version" => version}) do
     raise InvalidDocument,
       message: "JSON:API Object has invalid version (#{version})",
-      reference: "https://jsonapi.org/format/#document-jsonapi-object"
+      errors: [
+        %ErrorObject{
+          title: "JSON:API Object has invalid version (#{version})",
+          detail: "https://jsonapi.org/format/#document-jsonapi-object",
+          source: %{pointer: "/jsonapi/version"}
+        }
+      ]
   end
 
   defp deserialize_version(_data), do: nil
diff --git a/lib/jsonapi_plug/document/relationship_object.ex b/lib/jsonapi_plug/document/relationship_object.ex
index a477a61..89849a0 100644
--- a/lib/jsonapi_plug/document/relationship_object.ex
+++ b/lib/jsonapi_plug/document/relationship_object.ex
@@ -5,12 +5,9 @@ defmodule JSONAPIPlug.Document.RelationshipObject do
   https://jsonapi.org/format/#document-resource-object-relationships
   """
 
-  alias JSONAPIPlug.{
-    Document,
-    Document.LinkObject,
-    Document.ResourceIdentifierObject,
-    Exceptions.InvalidDocument
-  }
+  alias JSONAPIPlug.Document
+  alias JSONAPIPlug.Document.{ErrorObject, LinkObject, ResourceIdentifierObject}
+  alias JSONAPIPlug.Exceptions.InvalidDocument
 
   @type links :: %{atom() => LinkObject.t()}
 
@@ -54,8 +51,14 @@ defmodule JSONAPIPlug.Document.RelationshipObject do
 
   defp deserialize_meta(%{"meta" => _meta}) do
     raise InvalidDocument,
-      message: "Relationship object 'meta' must be an object",
-      reference: "https://jsonapi.org/format/#document-resource-object-relationships"
+      message: "Relationship Object 'meta' must be an object",
+      errors: [
+        %ErrorObject{
+          title: "Relationship Object 'meta' must be an object",
+          detail: "https://jsonapi.org/format/#document-resource-object-relationships",
+          source: %{pointer: "/meta"}
+        }
+      ]
   end
 
   defp deserialize_meta(_data), do: nil
diff --git a/lib/jsonapi_plug/document/resource_identifier_object.ex b/lib/jsonapi_plug/document/resource_identifier_object.ex
index ea86a00..094485f 100644
--- a/lib/jsonapi_plug/document/resource_identifier_object.ex
+++ b/lib/jsonapi_plug/document/resource_identifier_object.ex
@@ -5,7 +5,9 @@ defmodule JSONAPIPlug.Document.ResourceIdentifierObject do
   https://jsonapi.org/format/#document-resource-object-linkage
   """
 
-  alias JSONAPIPlug.{Document, Document.ResourceObject, Exceptions.InvalidDocument}
+  alias JSONAPIPlug.Document
+  alias JSONAPIPlug.Document.{ErrorObject, ResourceObject}
+  alias JSONAPIPlug.Exceptions.InvalidDocument
 
   @type t :: %__MODULE__{
           id: ResourceObject.id() | nil,
@@ -36,7 +38,12 @@ defmodule JSONAPIPlug.Document.ResourceIdentifierObject do
   defp deserialize_meta(%{"meta" => _meta}) do
     raise InvalidDocument,
       message: "Resource Identifier object 'meta' must be an object",
-      reference: "https://jsonapi.org/format/#document-resource-identifier-objects"
+      errors: [
+        %ErrorObject{
+          title: "Resource Identifier object 'meta' must be an object",
+          detail: "https://jsonapi.org/format/#document-resource-identifier-objects"
+        }
+      ]
   end
 
   defp deserialize_meta(_payload), do: nil
@@ -45,7 +52,12 @@ defmodule JSONAPIPlug.Document.ResourceIdentifierObject do
 
   defp deserialize_type(type) do
     raise InvalidDocument,
-      message: "Resource Identifier object type (#{type}) is invalid",
-      reference: "https://jsonapi.org/format/#document-resource-objects"
+      message: "Resource Identifier object type '#{type}' is invalid",
+      errors: [
+        %ErrorObject{
+          title: "Resource Identifier object type '#{type}' is invalid",
+          detail: "https://jsonapi.org/format/#document-resource-objects"
+        }
+      ]
   end
 end
diff --git a/lib/jsonapi_plug/document/resource_object.ex b/lib/jsonapi_plug/document/resource_object.ex
index 2036335..67b768e 100644
--- a/lib/jsonapi_plug/document/resource_object.ex
+++ b/lib/jsonapi_plug/document/resource_object.ex
@@ -5,21 +5,19 @@ defmodule JSONAPIPlug.Document.ResourceObject do
   https://jsonapi.org/format/#resource_object-resource-objects
   """
 
-  alias JSONAPIPlug.{
-    Document,
-    Document.LinkObject,
-    Document.RelationshipObject,
-    Exceptions.InvalidDocument
-  }
+  alias JSONAPIPlug.Document
+  alias JSONAPIPlug.Document.{ErrorObject, LinkObject, RelationshipObject}
+  alias JSONAPIPlug.Exceptions.InvalidDocument
 
   @type id :: String.t()
   @type type :: String.t()
+  @type attributes :: %{String.t() => Document.value()}
 
   @type t :: %__MODULE__{
           id: id() | nil,
           lid: id() | nil,
           type: type(),
-          attributes: %{String.t() => Document.value()},
+          attributes: attributes() | nil,
           links: Document.links() | nil,
           meta: Document.meta() | nil,
           relationships: %{String.t() => [RelationshipObject.t()]}
@@ -56,19 +54,34 @@ defmodule JSONAPIPlug.Document.ResourceObject do
   defp deserialize_type(%{"type" => type}) do
     raise InvalidDocument,
       message: "Resource object type '#{type}' is invalid",
-      reference: "https://jsonapi.org/format/#document-resource-objects"
+      errors: [
+        %ErrorObject{
+          title: "Resource object type (#{type}) is invalid",
+          detail: "https://jsonapi.org/format/#document-resource-objects"
+        }
+      ]
   end
 
   defp deserialize_attributes(%{"attributes" => %{"id" => _id}}) do
     raise InvalidDocument,
       message: "Resource object cannot have an attribute named 'id'",
-      reference: "https://jsonapi.org/format/#document-resource-objects"
+      errors: [
+        %ErrorObject{
+          title: "Resource object cannot have an attribute named 'id'",
+          detail: "https://jsonapi.org/format/#document-resource-objects"
+        }
+      ]
   end
 
   defp deserialize_attributes(%{"attributes" => %{"type" => _type}}) do
     raise InvalidDocument,
       message: "Resource object cannot have an attribute named 'type'",
-      reference: "https://jsonapi.org/format/#document-resource-objects"
+      errors: [
+        %ErrorObject{
+          title: "Resource object cannot have an attribute named 'type'",
+          detail: "https://jsonapi.org/format/#document-resource-objects"
+        }
+      ]
   end
 
   defp deserialize_attributes(%{"attributes" => attributes})
@@ -88,13 +101,23 @@ defmodule JSONAPIPlug.Document.ResourceObject do
   defp deserialize_relationships(%{"relationships" => %{"id" => _id}}) do
     raise InvalidDocument,
       message: "Resource object cannot have a relationship named 'id'",
-      reference: "https://jsonapi.org/format/#document-resource-objects"
+      errors: [
+        %ErrorObject{
+          title: "Resource object cannot have a relationship named 'id'",
+          detail: "https://jsonapi.org/format/#document-resource-objects"
+        }
+      ]
   end
 
   defp deserialize_relationships(%{"relationships" => %{"type" => _type}}) do
     raise InvalidDocument,
       message: "Resource object cannot have a relationship named 'type'",
-      reference: "https://jsonapi.org/format/#document-resource-objects"
+      errors: [
+        %ErrorObject{
+          title: "Resource object cannot have a relationship named 'type'",
+          detail: "https://jsonapi.org/format/#document-resource-objects"
+        }
+      ]
   end
 
   defp deserialize_relationships(%{"relationships" => relationships})
@@ -113,7 +136,12 @@ defmodule JSONAPIPlug.Document.ResourceObject do
        }) do
     raise InvalidDocument,
       message: "Resource object 'relationships' attribute must be an object",
-      reference: "https://jsonapi.org/format/#document-resource-object-relationships"
+      errors: [
+        %ErrorObject{
+          title: "Resource object 'relationships' attribute must be an object",
+          detail: "https://jsonapi.org/format/#document-resource-object-relationships"
+        }
+      ]
   end
 
   defp deserialize_relationships(_data), do: %{}
@@ -123,7 +151,12 @@ defmodule JSONAPIPlug.Document.ResourceObject do
   defp deserialize_meta(%{"meta" => _meta}) do
     raise InvalidDocument,
       message: "Resource object 'meta' must be an object",
-      reference: "https://jsonapi.org/format/#document-resource-objects"
+      errors: [
+        %ErrorObject{
+          title: "Resource object 'meta' must be an object",
+          detail: "https://jsonapi.org/format/#document-resource-objects"
+        }
+      ]
   end
 
   defp deserialize_meta(_data), do: nil
diff --git a/lib/jsonapi_plug/exceptions.ex b/lib/jsonapi_plug/exceptions.ex
index 9e5761e..a5da608 100644
--- a/lib/jsonapi_plug/exceptions.ex
+++ b/lib/jsonapi_plug/exceptions.ex
@@ -3,22 +3,40 @@ defmodule JSONAPIPlug.Exceptions do
 
   defmodule InvalidDocument do
     @moduledoc """
-    Defines a generic exception for when an invalid document is received.
+    Exception for when an invalid document is received.
     """
-    defexception message: nil, reference: nil
+    alias JSONAPIPlug.Document.ErrorObject
+    defexception message: nil, errors: nil
+
+    @default_error %ErrorObject{
+      status: "500",
+      title: "An error occurred while processing the request.",
+      detail: "Contact the system administrator for assitance."
+    }
 
     @spec exception(keyword()) :: Exception.t()
     def exception(options) do
-      message = Keyword.fetch!(options, :message)
-      reference = Keyword.fetch!(options, :reference)
+      message = List.first(options[:errors], @default_error).title
+
+      %__MODULE__{message: message, errors: options[:errors] || [@default_error]}
+    end
+  end
 
-      %__MODULE__{message: message, reference: reference}
+  defmodule InvalidAttributes do
+    @moduledoc """
+    Exception for when invalid resource attributes are received.
+    """
+    defexception message: nil, errors: nil
+
+    @spec exception(keyword()) :: Exception.t()
+    def exception(options) do
+      %__MODULE__{message: options[:message], errors: options[:errors]}
     end
   end
 
   defmodule InvalidHeader do
     @moduledoc """
-    Defines a generic exception for when an invalid header is received.
+    Exception for when an invalid header is received.
     """
     defexception header: nil, message: nil, reference: nil, status: nil
 
@@ -35,7 +53,7 @@ defmodule JSONAPIPlug.Exceptions do
 
   defmodule InvalidQuery do
     @moduledoc """
-    Defines a generic exception for when an invalid query parameter is received.
+    Exception for when an invalid query parameter is received.
     """
     defexception message: "invalid query",
                  type: nil,
diff --git a/lib/jsonapi_plug/normalizer.ex b/lib/jsonapi_plug/normalizer.ex
index 2324227..92be668 100644
--- a/lib/jsonapi_plug/normalizer.ex
+++ b/lib/jsonapi_plug/normalizer.ex
@@ -31,17 +31,15 @@ defmodule JSONAPIPlug.Normalizer do
   any point in your normalizer code.
   """
 
-  alias JSONAPIPlug.{
-    Document,
-    Document.RelationshipObject,
-    Document.ResourceIdentifierObject,
-    Document.ResourceObject,
-    Exceptions.InvalidDocument,
-    Pagination,
-    Resource,
-    Resource.Attribute,
-    Resource.Links,
-    Resource.Meta
+  alias JSONAPIPlug.{Document, Pagination, Resource}
+  alias JSONAPIPlug.Exceptions.{InvalidAttributes, InvalidDocument}
+  alias JSONAPIPlug.Resource.{Attribute, Links, Meta, Validator}
+
+  alias JSONAPIPlug.Document.{
+    ErrorObject,
+    RelationshipObject,
+    ResourceIdentifierObject,
+    ResourceObject
   }
 
   alias Plug.Conn
@@ -65,7 +63,7 @@ defmodule JSONAPIPlug.Normalizer do
             ) ::
               params() | no_return()
 
-  @doc "Transforms a JSON:API Document user data"
+  @doc "Transforms a JSON:API Document into user data"
   @spec denormalize(Document.t(), Resource.t(), Conn.t()) :: Conn.params() | no_return()
   def denormalize(%Document{data: nil}, _resource, _conn), do: %{}
 
@@ -115,7 +113,12 @@ defmodule JSONAPIPlug.Normalizer do
       {true, nil} ->
         raise InvalidDocument,
           message: "Resource ID not received in request and API requires Client-Generated IDs",
-          reference: "https://jsonapi.org/format/1.0/#crud-creating-client-ids"
+          errors: [
+            %ErrorObject{
+              title: "Resource ID not received in request and API requires Client-Generated IDs",
+              detail: "https://jsonapi.org/format/1.0/#crud-creating-client-ids"
+            }
+          ]
 
       {true, id} ->
         jsonapi_plug.config[:normalizer].denormalize_attribute(
@@ -129,21 +132,38 @@ defmodule JSONAPIPlug.Normalizer do
 
       {false, _id} ->
         raise InvalidDocument,
-          message: "Resource ID received in request and API forbids Client-Generated IDs",
-          reference: "https://jsonapi.org/format/1.0/#crud-creating-client-ids"
+          message: "Resource ID not received in request and API forbids Client-Generated IDs",
+          errors: [
+            %ErrorObject{
+              title: "Resource ID not received in request and API requires Client-Generated IDs",
+              detail: "https://jsonapi.org/format/1.0/#crud-creating-client-ids"
+            }
+          ]
     end
   end
 
-  defp denormalize_attributes(params, %ResourceObject{} = resource_object, resource, conn) do
-    Enum.reduce(Resource.attributes(resource), params, fn attribute, params ->
-      denormalize_attribute(
+  defp denormalize_attributes(
+         params,
+         %ResourceObject{} = resource_object,
+         resource,
+         conn
+       ) do
+    params =
+      Enum.reduce(
+        Resource.attributes(resource),
         params,
-        resource_object,
-        resource,
-        attribute,
-        conn
+        &denormalize_attribute(&2, resource_object, resource, &1, conn)
       )
-    end)
+
+    case Validator.validate(resource, params, conn) do
+      :ok ->
+        params
+
+      {:error, errors} ->
+        raise InvalidAttributes,
+          message: "Resource '#{Resource.type(resource)}' is invalid.",
+          errors: errors
+    end
   end
 
   defp denormalize_attribute(
@@ -224,13 +244,23 @@ defmodule JSONAPIPlug.Normalizer do
 
         {true, _related_data} ->
           raise InvalidDocument,
-            message: "Single resource for many relationship during normalization",
-            reference: nil
+            message: "Invalid value for '#{resource.type()}' relationship '#{name}'",
+            errors: [
+              %ErrorObject{
+                title: "Invalid value for '#{resource.type()}' relationship '#{name}'",
+                detail: "Relationship '#{name}' is one-to-many but a single value was received."
+              }
+            ]
 
         {false, %RelationshipObject{data: data}} when is_list(data) ->
           raise InvalidDocument,
-            message: "List of resources for one-to-one relationship during normalization",
-            reference: nil
+            message: "Invalid value for '#{resource.type()}' relationship '#{name}'",
+            errors: [
+              %ErrorObject{
+                title: "Invalid value for '#{resource.type()}' relationship '#{name}'",
+                detail: "Relationship '#{name}' is one-to-one but a list was received."
+              }
+            ]
 
         {false, %RelationshipObject{data: resource_identifier_object} = relationship_object} ->
           value =
@@ -370,13 +400,23 @@ defmodule JSONAPIPlug.Normalizer do
       case {related_many, related_resource} do
         {false, related_resources} when is_list(related_resources) ->
           raise InvalidDocument,
-            message: "List of resources given to render for one-to-one relationship",
-            reference: nil
+            message: "Invalid value for '#{Resource.type(resource)}' relationship '#{key}'",
+            errors: [
+              %ErrorObject{
+                title: "Invalid value for '#{Resource.type(resource)}' relationship '#{key}'",
+                detail: "Relationship '#{key}' is one-to-one but a list was received."
+              }
+            ]
 
         {true, _related_resource} when not is_list(related_resource) ->
           raise InvalidDocument,
-            message: "Single resource given to render for many relationship",
-            reference: nil
+            message: "Invalid value for '#{Resource.type(resource)}' relationship '#{key}'",
+            errors: [
+              %ErrorObject{
+                title: "Invalid value for '#{Resource.type(resource)}' relationship '#{key}'",
+                detail: "Relationship '#{key}' is one-to-many but a single value was received."
+              }
+            ]
 
         {_related_many, related_resource} ->
           {
@@ -469,6 +509,7 @@ defmodule JSONAPIPlug.Normalizer do
     related_data = Map.get(resource, relationship)
     related_loaded? = relationship_loaded?(related_data)
     related_many = Resource.field_option(resource, relationship, :many)
+    related_resource = struct(Resource.field_option(resource, relationship, :resource))
 
     case {related_loaded?, related_many, related_data} do
       {true, true, related_data} when is_list(related_data) ->
@@ -479,13 +520,28 @@ defmodule JSONAPIPlug.Normalizer do
 
       {true, _related_many, related_data} when is_list(related_data) ->
         raise InvalidDocument,
-          message: "List of resources given to render for one-to-one relationship",
-          reference: nil
+          message:
+            "Invalid value for '#{Resource.type(related_resource)}' relationship '#{relationship}'",
+          errors: [
+            %ErrorObject{
+              title:
+                "Invalid value for '#{Resource.type(related_resource)}' relationship '#{relationship}'",
+              detail: "Relationship '#{relationship}' is one-to-one but a list was received."
+            }
+          ]
 
       {true, true, _related_data} ->
         raise InvalidDocument,
-          message: "Single resource given to render for many relationship",
-          reference: nil
+          message:
+            "Invalid value for '#{Resource.type(related_resource)}' relationship '#{relationship}'",
+          errors: [
+            %ErrorObject{
+              title:
+                "Invalid value for '#{Resource.type(related_resource)}' relationship '#{relationship}'",
+              detail:
+                "Relationship '#{relationship}' is one-to-many but a single value was received."
+            }
+          ]
 
       {true, _related_many, _related_data} ->
         MapSet.put(
diff --git a/lib/jsonapi_plug/plug.ex b/lib/jsonapi_plug/plug.ex
index 75be5ef..2040670 100644
--- a/lib/jsonapi_plug/plug.ex
+++ b/lib/jsonapi_plug/plug.ex
@@ -142,33 +142,42 @@ defmodule JSONAPIPlug.Plug do
   end
 
   @impl Plug.ErrorHandler
+  def handle_errors(
+        conn,
+        %{kind: :error, reason: %Exceptions.InvalidAttributes{} = exception, stack: _stack}
+      ) do
+    send_errors(conn, :not_acceptable, exception.errors)
+  end
+
   def handle_errors(
         conn,
         %{kind: :error, reason: %Exceptions.InvalidDocument{} = exception, stack: _stack}
       ) do
-    send_error(conn, :bad_request, %Document.ErrorObject{
-      detail: "#{exception.message}. See #{exception.reference} for more information."
-    })
+    send_errors(conn, :bad_request, exception.errors)
   end
 
   def handle_errors(
         conn,
         %{kind: :error, reason: %Exceptions.InvalidHeader{} = exception, stack: _stack}
       ) do
-    send_error(conn, exception.status, %Document.ErrorObject{
-      detail: "#{exception.message}. See #{exception.reference} for more information.",
-      source: %{pointer: "/header/#{exception.header}"}
-    })
+    send_errors(conn, exception.status, [
+      %Document.ErrorObject{
+        detail: "#{exception.message}. See #{exception.reference} for more information.",
+        source: %{pointer: "/header/#{exception.header}"}
+      }
+    ])
   end
 
   def handle_errors(
         conn,
         %{kind: :error, reason: %Exceptions.InvalidQuery{} = exception, stack: _stack}
       ) do
-    send_error(conn, :bad_request, %Document.ErrorObject{
-      detail: exception.message,
-      source: %{pointer: "/query/#{exception.param}"}
-    })
+    send_errors(conn, :bad_request, [
+      %Document.ErrorObject{
+        detail: exception.message,
+        source: %{pointer: "/query/#{exception.param}"}
+      }
+    ])
   end
 
   def handle_errors(conn, error) do
@@ -176,19 +185,10 @@ defmodule JSONAPIPlug.Plug do
     send_resp(conn, 500, "Something went wrong")
   end
 
-  defp send_error(conn, code, %Document.ErrorObject{} = error) do
-    status_code = Conn.Status.code(code)
-
+  defp send_errors(conn, code, errors) do
     conn
     |> put_resp_content_type(JSONAPIPlug.mime_type())
-    |> send_resp(
-      code,
-      Jason.encode!(%Document{
-        errors: [
-          %{error | status: to_string(status_code), title: Conn.Status.reason_phrase(status_code)}
-        ]
-      })
-    )
+    |> send_resp(code, Jason.encode!(%Document{errors: errors}))
     |> halt()
   end
 
diff --git a/lib/jsonapi_plug/resource.ex b/lib/jsonapi_plug/resource.ex
index b41eb65..5e14cae 100644
--- a/lib/jsonapi_plug/resource.ex
+++ b/lib/jsonapi_plug/resource.ex
@@ -141,6 +141,14 @@ defprotocol JSONAPIPlug.Resource do
   @spec relationships(t()) :: [field_name()]
   def relationships(resource)
 
+  @doc """
+  Resource schema
+
+  Returns an ExJsonSchema used to validate resource attributes.
+  """
+  @spec schema(t()) :: term()
+  def schema(resource)
+
   @doc """
   Resource Type
 
@@ -155,6 +163,13 @@ defimpl JSONAPIPlug.Resource, for: Any do
     options =
       options
       |> Macro.prewalk(&Macro.expand(&1, __CALLER__))
+      |> Keyword.update(:attributes, [], fn attributes ->
+        Enum.map(attributes, fn
+          {field_name, nil} -> {field_name, []}
+          {field_name, field_options} -> {field_name, field_options}
+          field_name -> {field_name, []}
+        end)
+      end)
       |> NimbleOptions.validate!(JSONAPIPlug.resource_options_schema())
 
     attributes = generate_attributes(options)
@@ -163,7 +178,8 @@ defimpl JSONAPIPlug.Resource, for: Any do
     check_fields(attributes, relationships, options)
 
     field_option = generate_field_option(options)
-    recase_field = generate_recase_field(options)
+    recase_field = generate_recase_field(attributes, relationships)
+    schema = generate_schema(options)
 
     quote do
       defimpl JSONAPIPlug.Resource, for: unquote(module) do
@@ -182,23 +198,18 @@ defimpl JSONAPIPlug.Resource, for: Any do
         def path(_resource), do: unquote(options[:path])
         unquote(recase_field)
         def relationships(_resource), do: unquote(relationships)
+        def schema(_resource), do: unquote(schema)
         def type(_resource), do: unquote(options[:type])
       end
     end
   end
 
   defp generate_attributes(options) do
-    Enum.map(options[:attributes] || [], fn
-      {field_name, _field_options} -> field_name
-      field_name -> field_name
-    end)
+    Enum.map(options[:attributes] || [], fn {attribute, _options} -> attribute end)
   end
 
   defp generate_relationships(options) do
-    Enum.map(options[:relationships] || [], fn
-      {field_name, _field_options} -> field_name
-      field_name -> field_name
-    end)
+    Enum.map(options[:relationships] || [], fn {relationship, _options} -> relationship end)
   end
 
   defp check_fields(attributes, relationships, options) do
@@ -217,11 +228,6 @@ defimpl JSONAPIPlug.Resource, for: Any do
 
   defp generate_field_option(options) do
     Stream.concat(options[:attributes], options[:relationships])
-    |> Stream.map(fn
-      {field_name, nil} -> {field_name, []}
-      {field_name, field_options} -> {field_name, field_options}
-      field_name -> {field_name, []}
-    end)
     |> Enum.flat_map(fn {field_name, field_options} ->
       Enum.map(field_options, fn {field_option, value} ->
         quote do
@@ -232,22 +238,42 @@ defimpl JSONAPIPlug.Resource, for: Any do
     end)
   end
 
-  defp generate_recase_field(options) do
-    Stream.concat(options[:attributes], options[:relationships])
-    |> Stream.map(fn
-      {field_name, _field_options} -> field_name
-      field_name -> field_name
-    end)
+  defp generate_recase_field(attributes, relationships) do
+    Stream.concat(attributes, relationships)
     |> Enum.flat_map(fn field_name ->
       Enum.map([:camelize, :dasherize, :underscore], fn field_case ->
+        recased = JSONAPIPlug.recase(field_name, field_case)
+
         quote do
           def recase_field(_resource, unquote(field_name), unquote(field_case)),
-            do: unquote(JSONAPIPlug.recase(field_name, field_case))
+            do: unquote(recased)
+
+          def recase_field(_resource, unquote(to_string(field_name)), unquote(field_case)),
+            do: unquote(recased)
         end
       end)
     end)
   end
 
+  def generate_schema(options) do
+    %{
+      "type" => "object",
+      "required" =>
+        Enum.reduce(options[:attributes], [], fn {attribute, options}, required ->
+          (options[:required] && [to_string(options[:name] || attribute) | required]) || required
+        end),
+      "properties" =>
+        Enum.into(options[:attributes], %{}, fn {attribute, options} ->
+          {
+            to_string(options[:name] || attribute),
+            %{"type" => to_string(options[:type] || :string)}
+          }
+        end)
+    }
+    |> ExJsonSchema.Schema.resolve()
+    |> Macro.escape()
+  end
+
   def id_attribute(_resource), do: :id
   def attributes(_resource), do: []
   def field_name(_resource, field_name), do: field_name
@@ -255,5 +281,6 @@ defimpl JSONAPIPlug.Resource, for: Any do
   def path(_resource), do: nil
   def recase_field(_resource, field, _case), do: field
   def relationships(_resource), do: []
+  def schema(_resource), do: nil
   def type(_resource), do: ""
 end
diff --git a/lib/jsonapi_plug/resource/validator.ex b/lib/jsonapi_plug/resource/validator.ex
new file mode 100644
index 0000000..7c71296
--- /dev/null
+++ b/lib/jsonapi_plug/resource/validator.ex
@@ -0,0 +1,50 @@
+defprotocol JSONAPIPlug.Resource.Validator do
+  @moduledoc """
+  Resource Validator
+
+  Implement this protocol to validate a JSON:API resource.
+  Validation will be performed on resource attributes before normalizig them.
+
+  This example implementation always accepts params regardless of what is received.
+
+  ```elixir
+    defimpl JSONAPIPlug.Resource.Meta, for: MyApp.Post do
+      def validate(%@for{} = post, _params, _conn), do: :ok
+    end
+  ```
+  """
+
+  alias JSONAPIPlug.Document.{ErrorObject, ResourceObject}
+  alias JSONAPIPlug.Resource
+  alias Plug.Conn
+
+  @fallback_to_any true
+
+  @doc """
+  Validates the resource
+  """
+  @spec validate(Resource.t(), ResourceObject.attributes(), Conn.t()) ::
+          :ok | {:error, [ErrorObject.t()]}
+  def validate(resource, attributes, conn)
+end
+
+defimpl JSONAPIPlug.Resource.Validator, for: Any do
+  alias ExJsonSchema.Validator
+  alias JSONAPIPlug.Resource
+  alias JSONAPIPlug.Resource.Validator.ErrorFormatter
+  alias Plug.Conn
+
+  def validate(_resource, _attributes, %Conn{method: "PATCH"}), do: :ok
+
+  def validate(resource, attributes, %Conn{
+        private: %{jsonapi_plug: %JSONAPIPlug{} = jsonapi_plug}
+      }) do
+    case Validator.validate(Resource.schema(resource), attributes, error_formatter: false) do
+      :ok ->
+        :ok
+
+      {:error, errors} ->
+        {:error, ErrorFormatter.format(errors, resource, jsonapi_plug.config[:case])}
+    end
+  end
+end
diff --git a/lib/jsonapi_plug/resource/validator/error_formatter.ex b/lib/jsonapi_plug/resource/validator/error_formatter.ex
new file mode 100644
index 0000000..710aacf
--- /dev/null
+++ b/lib/jsonapi_plug/resource/validator/error_formatter.ex
@@ -0,0 +1,25 @@
+defmodule JSONAPIPlug.Resource.Validator.ErrorFormatter do
+  @moduledoc false
+
+  alias ExJsonSchema.Validator.Error
+  alias JSONAPIPlug.Document.ErrorObject
+  alias JSONAPIPlug.Resource
+
+  def format(errors, resource, case) do
+    Enum.flat_map(errors, fn %Error{error: error, path: "#" <> path} ->
+      format_error(error, resource, case, "/data/attributes/" <> path)
+    end)
+  end
+
+  defp format_error(%Error.Required{} = error, resource, case, base_path) do
+    Enum.map(error.missing, fn attribute ->
+      %ErrorObject{
+        title: "Campo obbligatorio",
+        detail: "Questo campo è obbligatorio.",
+        status: 422,
+        code: :unprocessable_entity,
+        source: %{pointer: base_path <> Resource.recase_field(resource, attribute, case)}
+      }
+    end)
+  end
+end
diff --git a/mix.exs b/mix.exs
index 7993a5d..63d25ca 100644
--- a/mix.exs
+++ b/mix.exs
@@ -40,6 +40,7 @@ defmodule JSONAPIPlug.Mixfile do
       {:credo, "~> 1.0", only: :dev, runtime: false},
       {:dialyxir, "~> 1.0", only: :dev, runtime: false},
       {:ex_doc, "~> 0.20", only: :dev, runtime: false},
+      {:ex_json_schema, "~> 0.10"},
       {:jason, "~> 1.0"},
       {:nimble_options, "~> 1.0"},
       {:plug, "~> 1.0"}
diff --git a/mix.lock b/mix.lock
index 64dc0ce..2294748 100644
--- a/mix.lock
+++ b/mix.lock
@@ -5,6 +5,7 @@
   "earmark_parser": {:hex, :earmark_parser, "1.4.44", "f20830dd6b5c77afe2b063777ddbbff09f9759396500cdbe7523efd58d7a339c", [:mix], [], "hexpm", "4778ac752b4701a5599215f7030989c989ffdc4f6df457c5f36938cc2d2a2750"},
   "erlex": {:hex, :erlex, "0.2.7", "810e8725f96ab74d17aac676e748627a07bc87eb950d2b83acd29dc047a30595", [:mix], [], "hexpm", "3ed95f79d1a844c3f6bf0cea61e0d5612a42ce56da9c03f01df538685365efb0"},
   "ex_doc": {:hex, :ex_doc, "0.38.2", "504d25eef296b4dec3b8e33e810bc8b5344d565998cd83914ffe1b8503737c02", [:mix], [{:earmark_parser, "~> 1.4.44", [hex: :earmark_parser, repo: "hexpm", optional: false]}, {:makeup_c, ">= 0.1.0", [hex: :makeup_c, repo: "hexpm", optional: true]}, {:makeup_elixir, "~> 0.14 or ~> 1.0", [hex: :makeup_elixir, repo: "hexpm", optional: false]}, {:makeup_erlang, "~> 0.1 or ~> 1.0", [hex: :makeup_erlang, repo: "hexpm", optional: false]}, {:makeup_html, ">= 0.1.0", [hex: :makeup_html, repo: "hexpm", optional: true]}], "hexpm", "732f2d972e42c116a70802f9898c51b54916e542cc50968ac6980512ec90f42b"},
+  "ex_json_schema": {:hex, :ex_json_schema, "0.10.2", "7c4b8c1481fdeb1741e2ce66223976edfb9bccebc8014f6aec35d4efe964fb71", [:mix], [{:decimal, "~> 2.0", [hex: :decimal, repo: "hexpm", optional: false]}], "hexpm", "37f43be60f8407659d4d0155a7e45e7f406dab1f827051d3d35858a709baf6a6"},
   "file_system": {:hex, :file_system, "1.1.0", "08d232062284546c6c34426997dd7ef6ec9f8bbd090eb91780283c9016840e8f", [:mix], [], "hexpm", "bfcf81244f416871f2a2e15c1b515287faa5db9c6bcf290222206d120b3d43f6"},
   "jason": {:hex, :jason, "1.4.4", "b9226785a9aa77b6857ca22832cffa5d5011a667207eb2a0ad56adb5db443b8a", [:mix], [{:decimal, "~> 1.0 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "c5eb0cab91f094599f94d55bc63409236a8ec69a21a67814529e8d5f6cc90b3b"},
   "makeup": {:hex, :makeup, "1.2.1", "e90ac1c65589ef354378def3ba19d401e739ee7ee06fb47f94c687016e3713d1", [:mix], [{:nimble_parsec, "~> 1.4", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "d36484867b0bae0fea568d10131197a4c2e47056a6fbe84922bf6ba71c8d17ce"},
diff --git a/test/jsonapi_plug/plug_test.exs b/test/jsonapi_plug/plug_test.exs
index 4f68e1c..8759715 100644
--- a/test/jsonapi_plug/plug_test.exs
+++ b/test/jsonapi_plug/plug_test.exs
@@ -226,7 +226,8 @@ defmodule JSONAPIPlug.PlugTest do
                    "data" => %{
                      "type" => "user",
                      "attributes" => %{
-                       "firstName" => "Jerome"
+                       "firstName" => "Jerome",
+                       "lastName" => "Finch"
                      },
                      "relationships" => %{
                        "company" => %{
@@ -263,7 +264,8 @@ defmodule JSONAPIPlug.PlugTest do
                      "lid" => "1",
                      "type" => "user",
                      "attributes" => %{
-                       "firstName" => "Jerome"
+                       "firstName" => "Jerome",
+                       "lastName" => "Finch"
                      },
                      "relationships" => %{
                        "company" => %{
diff --git a/test/support/resources.ex b/test/support/resources.ex
index aebd5cb..70eeec8 100644
--- a/test/support/resources.ex
+++ b/test/support/resources.ex
@@ -40,7 +40,7 @@ defmodule JSONAPIPlug.TestSupport.Resources do
       JSONAPIPlug.Resource,
       type: "user",
       attributes: [
-        age: nil,
+        age: [type: :number],
         first_name: nil,
         last_name: nil,
         full_name: [deserialize: false],