diff --git a/src/Observability/Runtime/docs/schemas/EXAMPLES.md b/src/Observability/Runtime/docs/schemas/EXAMPLES.md
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+# A365 Input/Output Message Schema Examples
+
+> **A365 Schema Version:** 1.0.0 | **Based on OTel Semconv:** v1.40.0
+
+---
+
+## Input Message Examples (`gen_ai.input.messages`)
+
+### Simple — Text Chat
+
+```json
+[
+  {
+    "role": "system",
+    "parts": [
+      { "type": "text", "content": "You are a helpful assistant." }
+    ]
+  },
+  {
+    "role": "user",
+    "parts": [
+      { "type": "text", "content": "What meetings do I have today?" }
+    ]
+  }
+]
+```
+
+### Complex — All Input Part Types
+
+A multi-turn conversation demonstrating every input part type: text, tool_call (from prior assistant turn), tool_call_response, server_tool_call, server_tool_call_response, blob, file, uri, reasoning, and a custom generic part.
+
+```json
+[
+  {
+    "role": "system",
+    "parts": [
+      { "type": "text", "content": "You are a project assistant with access to tools, files, and images." }
+    ],
+    "name": "OrchestratorAgent"
+  },
+  {
+    "role": "user",
+    "parts": [
+      { "type": "text", "content": "Summarize the attached document, check the weather in Seattle, and describe the whiteboard photo." },
+      {
+        "type": "file",
+        "modality": "image",
+        "mime_type": "application/pdf",
+        "file_id": "file-report-q1-2026"
+      },
+      {
+        "type": "uri",
+        "modality": "image",
+        "mime_type": "image/png",
+        "uri": "https://sharepoint.com/sites/team/whiteboard-photo.png"
+      },
+      {
+        "type": "blob",
+        "modality": "audio",
+        "mime_type": "audio/wav",
+        "content": "/9j/4AAQSkZJRg..."
+      }
+    ],
+    "name": "UserJohnDoe"
+  },
+  {
+    "role": "assistant",
+    "parts": [
+      { "type": "text", "content": "Let me look up the weather and analyze your files." },
+      {
+        "type": "tool_call",
+        "id": "call_weather_001",
+        "name": "get_weather",
+        "arguments": { "city": "Seattle", "units": "fahrenheit" }
+      },
+      {
+        "type": "reasoning",
+        "content": "User attached a PDF, an image URI, and an audio blob. I should process the weather tool call first, then analyze the attachments."
+      }
+    ]
+  },
+  {
+    "role": "tool",
+    "parts": [
+      {
+        "type": "tool_call_response",
+        "id": "call_weather_001",
+        "response": { "temperature": 57, "condition": "rainy", "humidity": 82 }
+      }
+    ]
+  },
+  {
+    "role": "assistant",
+    "parts": [
+      {
+        "type": "server_tool_call",
+        "id": "stc_code_001",
+        "name": "code_interpreter",
+        "server_tool_call": {
+          "type": "code_interpreter",
+          "code": "import pandas as pd\ndf = pd.read_csv('sales.csv')\nprint(df.describe())"
+        }
+      },
+      {
+        "type": "server_tool_call_response",
+        "id": "stc_code_001",
+        "server_tool_call_response": {
+          "type": "code_interpreter",
+          "output": "count: 1200, mean: 45000, max: 120000"
+        }
+      }
+    ]
+  },
+  {
+    "role": "user",
+    "parts": [
+      {
+        "type": "microsoft.a365.adaptive_card",
+        "card_id": "ac-approval-001",
+        "action": "approved"
+      }
+    ],
+    "name": "UserJohnDoe"
+  }
+]
+```
+
+**Part types demonstrated:**
+
+| Part Type | Where Used | Description |
+|---|---|---|
+| `text` | system, user, assistant | Plain text messages |
+| `tool_call` | assistant (prior turn) | Model requested a client-side tool |
+| `tool_call_response` | tool | Client-side tool result sent back |
+| `server_tool_call` | assistant (prior turn) | Server-side tool invocation |
+| `server_tool_call_response` | assistant (prior turn) | Server-side tool result |
+| `blob` | user | Inline binary data (base64) |
+| `file` | user | Pre-uploaded file reference |
+| `uri` | user | External file by URL |
+| `reasoning` | assistant (prior turn) | Chain-of-thought from model |
+| `microsoft.a365.adaptive_card` | user | Custom A365 GenericPart |
+
+---
+
+## Output Message Examples (`gen_ai.output.messages`)
+
+### Simple — Text Response
+
+```json
+[
+  {
+    "role": "assistant",
+    "finish_reason": "stop",
+    "parts": [
+      { "type": "text", "content": "You have 3 meetings today: standup at 9 AM, design review at 11 AM, and a 1:1 at 3 PM." }
+    ]
+  }
+]
+```
+
+### Complex — All Output Part Types
+
+A response demonstrating every output part type: reasoning, text, tool_call, server_tool_call with response, and a custom generic part. Also shows multiple finish reasons.
+
+```json
+[
+  {
+    "role": "assistant",
+    "finish_reason": "stop",
+    "parts": [
+      {
+        "type": "reasoning",
+        "content": "The user asked for a document summary, weather, and whiteboard analysis. I have the weather data from the tool call. The code_interpreter analyzed the sales data. I should compile all results into a structured response."
+      },
+      {
+        "type": "text",
+        "content": "Here's your summary:\n\n**Weather:** Seattle is currently rainy at 57°F with 82% humidity.\n\n**Q1 Report:** Revenue averaged $45K per deal across 1,200 transactions, with a max deal of $120K.\n\n**Whiteboard:** The whiteboard shows a system architecture diagram with three microservices connected via an API gateway."
+      },
+      {
+        "type": "server_tool_call",
+        "id": "stc_search_001",
+        "name": "web_search",
+        "server_tool_call": {
+          "type": "web_search",
+          "query": "Seattle weather forecast March 2026"
+        }
+      },
+      {
+        "type": "server_tool_call_response",
+        "id": "stc_search_001",
+        "server_tool_call_response": {
+          "type": "web_search",
+          "results": [
+            { "title": "Seattle Weather - March 2026", "url": "https://weather.com/seattle", "snippet": "Expect rain through the week..." }
+          ]
+        }
+      },
+      {
+        "type": "blob",
+        "modality": "image",
+        "mime_type": "image/png",
+        "content": "iVBORw0KGgoAAAANSUhEUg..."
+      },
+      {
+        "type": "uri",
+        "modality": "image",
+        "mime_type": "image/png",
+        "uri": "https://ai-generated.example.com/chart-q1-revenue.png"
+      }
+    ],
+    "name": "ProjectAssistant"
+  }
+]
+```
+
+**Additional output examples by finish reason:**
+
+#### Tool Call Request
+
+```json
+[
+  {
+    "role": "assistant",
+    "finish_reason": "tool_call",
+    "parts": [
+      { "type": "text", "content": "Let me check that for you." },
+      {
+        "type": "tool_call",
+        "id": "call_sales_q1",
+        "name": "query_sales_data",
+        "arguments": { "quarter": "Q1", "year": 2026 }
+      },
+      {
+        "type": "tool_call",
+        "id": "call_calendar",
+        "name": "get_calendar",
+        "arguments": { "date": "2026-03-25" }
+      }
+    ]
+  }
+]
+```
+
+#### Content Filter
+
+```json
+[
+  {
+    "role": "assistant",
+    "finish_reason": "content_filter",
+    "parts": [
+      { "type": "text", "content": "I'm unable to provide that information due to content policy restrictions." }
+    ]
+  }
+]
+```
+
+#### Token Limit
+
+```json
+[
+  {
+    "role": "assistant",
+    "finish_reason": "length",
+    "parts": [
+      { "type": "text", "content": "Here is the beginning of the report: Q1 revenue increased by 15% year-over-year driven by strong adoption of..." }
+    ]
+  }
+]
+```
+
+#### Error
+
+```json
+[
+  {
+    "role": "assistant",
+    "finish_reason": "error",
+    "parts": [
+      { "type": "text", "content": "An error occurred while processing your request. Please try again." }
+    ]
+  }
+]
+```
+
+**Part types demonstrated in output:**
+
+| Part Type | Description |
+|---|---|
+| `text` | Direct text response from model |
+| `reasoning` | Chain-of-thought / thinking content |
+| `tool_call` | Model requesting client-side tool execution |
+| `server_tool_call` | Server-side tool invocation details |
+| `server_tool_call_response` | Server-side tool result |
+| `blob` | Generated binary content (e.g., chart image) |
+| `uri` | Reference to generated content |
+
+**Finish reasons demonstrated:**
+
+| Finish Reason | Meaning |
+|---|---|
+| `stop` | Model completed naturally |
+| `tool_call` | Model is requesting tool execution |
+| `content_filter` | Blocked by content policy |
+| `length` | Token limit exceeded |
+| `error` | Generation encountered an error |
diff --git a/src/Observability/Runtime/docs/schemas/SCHEMA-VERSION.md b/src/Observability/Runtime/docs/schemas/SCHEMA-VERSION.md
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+# A365 Observability Input/Output Message Schema Versions
+
+## Current Version
+
+| Field | Value |
+|---|---|
+| **A365 Schema Version** | 1.0.0 |
+| **OTel Semconv Baseline** | [v1.40.0](https://github.com/open-telemetry/semantic-conventions/tree/v1.40.0) |
+| **OTel Semconv Commit** | [`30003a993`](https://github.com/open-telemetry/semantic-conventions/commit/30003a9937eb7bcde6984877149055278405e03c) |
+
+## Schema Files
+
+| File | Span Attribute | Description |
+|---|---|---|
+| [a365-input-messages.json](a365-input-messages.json) | `gen_ai.input.messages` | Chat history sent to the model |
+| [a365-output-messages.json](a365-output-messages.json) | `gen_ai.output.messages` | Model response (choices/candidates) |
+
+## OTel Semconv Compatibility Matrix
+
+| A365 Schema Version | Based on OTel Semconv | Part Types | Notes |
+|---|---|---|---|
+| 1.0.0 | v1.40.0 | 10 (all OTel types) | Initial release. Includes ServerToolCall parts added in v1.40.0 |
+
+### OTel Input/Output Schema Change History (for reference)
+
+| OTel Semconv | File SHA (input) | Changes from Previous |
+|---|---|---|
+| v1.36.0 | — | Schema files did not exist |
+| v1.37.0 | `22910f30` | **Schema introduced.** 4 part types: Text, ToolCallRequest, ToolCallResponse, Generic. No `name` field. |
+| v1.38.0 | `5fbd431f` | **Major expansion.** Added Blob, File, Uri, Reasoning parts. Added Modality enum. Added `name` field to ChatMessage. |
+| v1.39.0 | `5fbd431f` | No changes (identical to v1.38.0) |
+| v1.40.0 | `5585531c` | Added ServerToolCallPart, ServerToolCallResponsePart. Minor wording fix. |
+
+## Applicable Scopes
+
+| A365 Scope | Uses This Schema? | Notes |
+|---|---|---|
+| `InvokeAgentScope` | ✅ | Full conversation context |
+| `InferenceScope` | ✅ | Chat history + model response |
+| `OutputScope` | ✅ | Outgoing messages to user |
+| `ExecuteToolScope` | ❌ | Uses `gen_ai.tool.*` attributes instead |
+
+## Changelog
+
+### 1.0.0
+
+- Initial A365 input/output message schema
+- Profiles OTel GenAI semconv v1.40.0 input/output messages format
+- Supports all OTel part types: TextPart, ToolCallRequestPart, ToolCallResponsePart, ServerToolCallPart, ServerToolCallResponsePart, BlobPart, FilePart, UriPart, ReasoningPart, GenericPart
+- All objects allow `additionalProperties` for future A365-specific extensions
+- Custom A365 part types can be added via `GenericPart` using `microsoft.a365.*` type prefix
diff --git a/src/Observability/Runtime/docs/schemas/a365-input-messages.json b/src/Observability/Runtime/docs/schemas/a365-input-messages.json
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+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://microsoft.com/agents/a365/observability/schemas/input-messages",
+  "title": "A365 Input Messages",
+  "description": "A365 Observability input message schema for the gen_ai.input.messages span attribute. Profiles the OTel GenAI semantic conventions input messages format.",
+  "a365_schema_version": "1.0.0",
+  "otel_semconv_baseline": "v1.40.0",
+  "otel_semconv_commit": "30003a9937eb7bcde6984877149055278405e03c",
+
+  "type": "array",
+  "items": {
+    "$ref": "#/$defs/ChatMessage"
+  },
+
+  "$defs": {
+    "Role": {
+      "description": "Role of the entity that created the message.",
+      "enum": ["system", "user", "assistant", "tool"],
+      "type": "string"
+    },
+
+    "Modality": {
+      "description": "The general modality of media content.",
+      "enum": ["image", "video", "audio"],
+      "type": "string"
+    },
+
+    "ChatMessage": {
+      "description": "Represents a single message in the chat history sent to the model.",
+      "type": "object",
+      "additionalProperties": true,
+      "required": ["role", "parts"],
+      "properties": {
+        "role": {
+          "anyOf": [{ "$ref": "#/$defs/Role" }, { "type": "string" }],
+          "description": "Role of the entity that created the message."
+        },
+        "parts": {
+          "description": "List of message parts that make up the message content.",
+          "type": "array",
+          "items": {
+            "anyOf": [
+              { "$ref": "#/$defs/TextPart" },
+              { "$ref": "#/$defs/ToolCallRequestPart" },
+              { "$ref": "#/$defs/ToolCallResponsePart" },
+              { "$ref": "#/$defs/ServerToolCallPart" },
+              { "$ref": "#/$defs/ServerToolCallResponsePart" },
+              { "$ref": "#/$defs/BlobPart" },
+              { "$ref": "#/$defs/FilePart" },
+              { "$ref": "#/$defs/UriPart" },
+              { "$ref": "#/$defs/ReasoningPart" },
+              { "$ref": "#/$defs/GenericPart" }
+            ]
+          }
+        },
+        "name": {
+          "anyOf": [{ "type": "string" }, { "type": "null" }],
+          "default": null,
+          "description": "The name of the participant."
+        }
+      }
+    },
+
+    "TextPart": {
+      "description": "Represents text content sent to the model.",
+      "type": "object",
+      "additionalProperties": true,
+      "required": ["type", "content"],
+      "properties": {
+        "type": { "const": "text" },
+        "content": { "type": "string", "description": "Text content sent to the model." }
+      }
+    },
+
+    "ToolCallRequestPart": {
+      "description": "Represents a tool call requested by the model.",
+      "type": "object",
+      "additionalProperties": true,
+      "required": ["type", "name"],
+      "properties": {
+        "type": { "const": "tool_call" },
+        "id": { "anyOf": [{ "type": "string" }, { "type": "null" }], "default": null, "description": "Unique identifier for the tool call." },
+        "name": { "type": "string", "description": "Name of the tool." },
+        "arguments": { "default": null, "description": "Arguments for the tool call." }
+      }
+    },
+
+    "ToolCallResponsePart": {
+      "description": "Represents a tool call result sent to the model.",
+      "type": "object",
+      "additionalProperties": true,
+      "required": ["type", "response"],
+      "properties": {
+        "type": { "const": "tool_call_response" },
+        "id": { "anyOf": [{ "type": "string" }, { "type": "null" }], "default": null, "description": "Unique tool call identifier." },
+        "response": { "description": "Tool call response." }
+      }
+    },
+
+    "ServerToolCallPart": {
+      "description": "Represents a server-side tool call invocation (e.g., code_interpreter, web_search).",
+      "type": "object",
+      "additionalProperties": true,
+      "required": ["type", "name", "server_tool_call"],
+      "properties": {
+        "type": { "const": "server_tool_call" },
+        "id": { "anyOf": [{ "type": "string" }, { "type": "null" }], "default": null },
+        "name": { "type": "string", "description": "Name of the server tool." },
+        "server_tool_call": { "description": "Server tool call details.", "type": "object", "additionalProperties": true, "required": ["type"], "properties": { "type": { "type": "string" } } }
+      }
+    },
+
+    "ServerToolCallResponsePart": {
+      "description": "Represents a server-side tool call response.",
+      "type": "object",
+      "additionalProperties": true,
+      "required": ["type", "server_tool_call_response"],
+      "properties": {
+        "type": { "const": "server_tool_call_response" },
+        "id": { "anyOf": [{ "type": "string" }, { "type": "null" }], "default": null },
+        "server_tool_call_response": { "description": "Server tool call response details.", "type": "object", "additionalProperties": true, "required": ["type"], "properties": { "type": { "type": "string" } } }
+      }
+    },
+
+    "BlobPart": {
+      "description": "Represents blob binary data sent inline to the model.",
+      "type": "object",
+      "additionalProperties": true,
+      "required": ["type", "modality", "content"],
+      "properties": {
+        "type": { "const": "blob" },
+        "mime_type": { "anyOf": [{ "type": "string" }, { "type": "null" }], "default": null, "description": "IANA MIME type." },
+        "modality": { "anyOf": [{ "$ref": "#/$defs/Modality" }, { "type": "string" }], "description": "General modality of the data." },
+        "content": { "type": "string", "format": "binary", "description": "Base64-encoded binary data." }
+      }
+    },
+
+    "FilePart": {
+      "description": "Represents an external file sent to the model by file ID.",
+      "type": "object",
+      "additionalProperties": true,
+      "required": ["type", "modality", "file_id"],
+      "properties": {
+        "type": { "const": "file" },
+        "mime_type": { "anyOf": [{ "type": "string" }, { "type": "null" }], "default": null },
+        "modality": { "anyOf": [{ "$ref": "#/$defs/Modality" }, { "type": "string" }] },
+        "file_id": { "type": "string", "description": "Identifier referencing a pre-uploaded file." }
+      }
+    },
+
+    "UriPart": {
+      "description": "Represents an external file sent to the model by URI.",
+      "type": "object",
+      "additionalProperties": true,
+      "required": ["type", "modality", "uri"],
+      "properties": {
+        "type": { "const": "uri" },
+        "mime_type": { "anyOf": [{ "type": "string" }, { "type": "null" }], "default": null },
+        "modality": { "anyOf": [{ "$ref": "#/$defs/Modality" }, { "type": "string" }] },
+        "uri": { "type": "string", "description": "URI referencing attached data." }
+      }
+    },
+
+    "ReasoningPart": {
+      "description": "Represents reasoning/thinking content from the model.",
+      "type": "object",
+      "additionalProperties": true,
+      "required": ["type", "content"],
+      "properties": {
+        "type": { "const": "reasoning" },
+        "content": { "type": "string", "description": "Reasoning/thinking content." }
+      }
+    },
+
+    "GenericPart": {
+      "description": "Represents an arbitrary message part for extensibility with custom types.",
+      "type": "object",
+      "additionalProperties": true,
+      "required": ["type"],
+      "properties": {
+        "type": { "type": "string", "description": "Custom part type identifier." }
+      }
+    }
+  }
+}
diff --git a/src/Observability/Runtime/docs/schemas/a365-output-messages.json b/src/Observability/Runtime/docs/schemas/a365-output-messages.json
new file mode 100644
index 00000000..92820e21
--- /dev/null
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@@ -0,0 +1,195 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://microsoft.com/agents/a365/observability/schemas/output-messages",
+  "title": "A365 Output Messages",
+  "description": "A365 Observability output message schema for the gen_ai.output.messages span attribute. Profiles the OTel GenAI semantic conventions output messages format.",
+  "a365_schema_version": "1.0.0",
+  "otel_semconv_baseline": "v1.40.0",
+  "otel_semconv_commit": "30003a9937eb7bcde6984877149055278405e03c",
+
+  "type": "array",
+  "items": {
+    "$ref": "#/$defs/OutputMessage"
+  },
+
+  "$defs": {
+    "Role": {
+      "description": "Role of the entity that created the message.",
+      "enum": ["system", "user", "assistant", "tool"],
+      "type": "string"
+    },
+
+    "FinishReason": {
+      "description": "Reason for finishing the generation.",
+      "enum": ["stop", "length", "content_filter", "tool_call", "error"],
+      "type": "string"
+    },
+
+    "Modality": {
+      "description": "The general modality of media content.",
+      "enum": ["image", "video", "audio"],
+      "type": "string"
+    },
+
+    "OutputMessage": {
+      "description": "Represents an output message generated by the model or agent. Each message corresponds to exactly one generation (choice/candidate).",
+      "type": "object",
+      "additionalProperties": true,
+      "required": ["role", "parts", "finish_reason"],
+      "properties": {
+        "role": {
+          "anyOf": [{ "$ref": "#/$defs/Role" }, { "type": "string" }],
+          "description": "Role of the entity that created the message."
+        },
+        "parts": {
+          "description": "List of message parts that make up the message content.",
+          "type": "array",
+          "items": {
+            "anyOf": [
+              { "$ref": "#/$defs/TextPart" },
+              { "$ref": "#/$defs/ToolCallRequestPart" },
+              { "$ref": "#/$defs/ToolCallResponsePart" },
+              { "$ref": "#/$defs/ServerToolCallPart" },
+              { "$ref": "#/$defs/ServerToolCallResponsePart" },
+              { "$ref": "#/$defs/BlobPart" },
+              { "$ref": "#/$defs/FilePart" },
+              { "$ref": "#/$defs/UriPart" },
+              { "$ref": "#/$defs/ReasoningPart" },
+              { "$ref": "#/$defs/GenericPart" }
+            ]
+          }
+        },
+        "name": {
+          "anyOf": [{ "type": "string" }, { "type": "null" }],
+          "default": null,
+          "description": "The name of the participant."
+        },
+        "finish_reason": {
+          "anyOf": [{ "$ref": "#/$defs/FinishReason" }, { "type": "string" }],
+          "description": "Reason for finishing the generation."
+        }
+      }
+    },
+
+    "TextPart": {
+      "description": "Represents text content received from the model.",
+      "type": "object",
+      "additionalProperties": true,
+      "required": ["type", "content"],
+      "properties": {
+        "type": { "const": "text" },
+        "content": { "type": "string", "description": "Text content from the model." }
+      }
+    },
+
+    "ToolCallRequestPart": {
+      "description": "Represents a tool call requested by the model.",
+      "type": "object",
+      "additionalProperties": true,
+      "required": ["type", "name"],
+      "properties": {
+        "type": { "const": "tool_call" },
+        "id": { "anyOf": [{ "type": "string" }, { "type": "null" }], "default": null, "description": "Unique identifier for the tool call." },
+        "name": { "type": "string", "description": "Name of the tool." },
+        "arguments": { "default": null, "description": "Arguments for the tool call." }
+      }
+    },
+
+    "ToolCallResponsePart": {
+      "description": "Represents a tool call result.",
+      "type": "object",
+      "additionalProperties": true,
+      "required": ["type", "response"],
+      "properties": {
+        "type": { "const": "tool_call_response" },
+        "id": { "anyOf": [{ "type": "string" }, { "type": "null" }], "default": null, "description": "Unique tool call identifier." },
+        "response": { "description": "Tool call response." }
+      }
+    },
+
+    "ServerToolCallPart": {
+      "description": "Represents a server-side tool call invocation (e.g., code_interpreter, web_search).",
+      "type": "object",
+      "additionalProperties": true,
+      "required": ["type", "name", "server_tool_call"],
+      "properties": {
+        "type": { "const": "server_tool_call" },
+        "id": { "anyOf": [{ "type": "string" }, { "type": "null" }], "default": null },
+        "name": { "type": "string", "description": "Name of the server tool." },
+        "server_tool_call": { "description": "Server tool call details.", "type": "object", "additionalProperties": true, "required": ["type"], "properties": { "type": { "type": "string" } } }
+      }
+    },
+
+    "ServerToolCallResponsePart": {
+      "description": "Represents a server-side tool call response.",
+      "type": "object",
+      "additionalProperties": true,
+      "required": ["type", "server_tool_call_response"],
+      "properties": {
+        "type": { "const": "server_tool_call_response" },
+        "id": { "anyOf": [{ "type": "string" }, { "type": "null" }], "default": null },
+        "server_tool_call_response": { "description": "Server tool call response details.", "type": "object", "additionalProperties": true, "required": ["type"], "properties": { "type": { "type": "string" } } }
+      }
+    },
+
+    "BlobPart": {
+      "description": "Represents blob binary data sent inline.",
+      "type": "object",
+      "additionalProperties": true,
+      "required": ["type", "modality", "content"],
+      "properties": {
+        "type": { "const": "blob" },
+        "mime_type": { "anyOf": [{ "type": "string" }, { "type": "null" }], "default": null, "description": "IANA MIME type." },
+        "modality": { "anyOf": [{ "$ref": "#/$defs/Modality" }, { "type": "string" }], "description": "General modality of the data." },
+        "content": { "type": "string", "format": "binary", "description": "Base64-encoded binary data." }
+      }
+    },
+
+    "FilePart": {
+      "description": "Represents an external file by file ID.",
+      "type": "object",
+      "additionalProperties": true,
+      "required": ["type", "modality", "file_id"],
+      "properties": {
+        "type": { "const": "file" },
+        "mime_type": { "anyOf": [{ "type": "string" }, { "type": "null" }], "default": null },
+        "modality": { "anyOf": [{ "$ref": "#/$defs/Modality" }, { "type": "string" }] },
+        "file_id": { "type": "string", "description": "Identifier referencing a pre-uploaded file." }
+      }
+    },
+
+    "UriPart": {
+      "description": "Represents an external file by URI.",
+      "type": "object",
+      "additionalProperties": true,
+      "required": ["type", "modality", "uri"],
+      "properties": {
+        "type": { "const": "uri" },
+        "mime_type": { "anyOf": [{ "type": "string" }, { "type": "null" }], "default": null },
+        "modality": { "anyOf": [{ "$ref": "#/$defs/Modality" }, { "type": "string" }] },
+        "uri": { "type": "string", "description": "URI referencing attached data." }
+      }
+    },
+
+    "ReasoningPart": {
+      "description": "Represents reasoning/thinking content from the model.",
+      "type": "object",
+      "additionalProperties": true,
+      "required": ["type", "content"],
+      "properties": {
+        "type": { "const": "reasoning" },
+        "content": { "type": "string", "description": "Reasoning/thinking content." }
+      }
+    },
+
+    "GenericPart": {
+      "description": "Represents an arbitrary message part for extensibility with custom types.",
+      "type": "object",
+      "additionalProperties": true,
+      "required": ["type"],
+      "properties": {
+        "type": { "type": "string", "description": "Custom part type identifier." }
+      }
+    }
+  }
+}