diff --git a/backend/app/core/exception_handlers.py b/backend/app/core/exception_handlers.py
index f6166b1..3164d35 100644
--- a/backend/app/core/exception_handlers.py
+++ b/backend/app/core/exception_handlers.py
@@ -8,12 +8,45 @@
 
 from app.utils import APIResponse
 
+def _format_validation_errors(errors: list[dict]) -> str:
+    missing_fields = []
+    invalid_fields = []
+
+    for err in errors:
+        loc = [x for x in err["loc"] if x != "body"]
+
+        if not loc:
+            continue
+
+        field = ".".join(str(x) for x in loc)
+
+        if err["msg"] == "Field required":
+            missing_fields.append(field)
+        else:
+            invalid_fields.append(f"{field} ({err['msg']})")
+
+    messages = []
+
+    if missing_fields:
+        messages.append(
+            f"Missing required field(s): {', '.join(missing_fields)}"
+        )
+
+    if invalid_fields:
+        messages.append(
+            f"Invalid field(s): {', '.join(invalid_fields)}"
+        )
+
+    return ". ".join(messages)
+
+
 def register_exception_handlers(app: FastAPI):
     @app.exception_handler(RequestValidationError)
     async def validation_error_handler(request: Request, exc: RequestValidationError):
+        formatted_message = _format_validation_errors(exc.errors())
         return JSONResponse(
             status_code=HTTP_422_UNPROCESSABLE_ENTITY,
-            content=APIResponse.failure_response(exc.errors()).model_dump(),
+            content=APIResponse.failure_response(error=formatted_message).model_dump(),
         )
 
     @app.exception_handler(HTTPException)
diff --git a/backend/app/models/base_validator_config.py b/backend/app/models/base_validator_config.py
index f4a2345..d9b051a 100644
--- a/backend/app/models/base_validator_config.py
+++ b/backend/app/models/base_validator_config.py
@@ -1,5 +1,6 @@
 from guardrails import OnFailAction
 from guardrails.validators import Validator
+from pydantic import ConfigDict
 from sqlmodel import SQLModel
 
 from app.core.enum import GuardrailOnFail
@@ -13,9 +14,12 @@
 }
 
 class BaseValidatorConfig(SQLModel):
-    on_fail: GuardrailOnFail = GuardrailOnFail.Fix
+    model_config = ConfigDict(
+        extra="forbid",
+        arbitrary_types_allowed=True
+    )
 
-    model_config = {"arbitrary_types_allowed": True}
+    on_fail: GuardrailOnFail = GuardrailOnFail.Fix
 
     def resolve_on_fail(self):
         try:
diff --git a/backend/app/models/guardrail_config.py b/backend/app/models/guardrail_config.py
index bfe36a6..1da302d 100644
--- a/backend/app/models/guardrail_config.py
+++ b/backend/app/models/guardrail_config.py
@@ -1,6 +1,7 @@
 from typing import Annotated, List, Optional, Union
 from uuid import UUID
 
+from pydantic import ConfigDict
 from sqlmodel import Field, SQLModel
 
 # todo this could be improved by having some auto-discovery mechanism inside
@@ -22,6 +23,7 @@
 ]
 
 class GuardrailRequest(SQLModel):
+    model_config = ConfigDict(extra="forbid")
     request_id: str
     input: str
     validators: List[ValidatorConfigItem]