feat: add MCP tool signature to Responses API (#2232)

docs/_static/llama-stack-spec.yaml

@@ -4762,12 +4762,14 @@ components:
         - $ref: '#/components/schemas/OpenAIResponseInputToolWebSearch'
         - $ref: '#/components/schemas/OpenAIResponseInputToolFileSearch'
         - $ref: '#/components/schemas/OpenAIResponseInputToolFunction'
+        - $ref: '#/components/schemas/OpenAIResponseInputToolMCP'
       discriminator:
         propertyName: type
         mapping:
           web_search: '#/components/schemas/OpenAIResponseInputToolWebSearch'
           file_search: '#/components/schemas/OpenAIResponseInputToolFileSearch'
           function: '#/components/schemas/OpenAIResponseInputToolFunction'
+          mcp: '#/components/schemas/OpenAIResponseInputToolMCP'
     OpenAIResponseInputToolFileSearch:
       type: object
       properties:
@@ -4822,6 +4824,66 @@ components:
         - type
         - name
       title: OpenAIResponseInputToolFunction
+    OpenAIResponseInputToolMCP:
+      type: object
+      properties:
+        type:
+          type: string
+          const: mcp
+          default: mcp
+        server_label:
+          type: string
+        server_url:
+          type: string
+        headers:
+          type: object
+          additionalProperties:
+            oneOf:
+              - type: 'null'
+              - type: boolean
+              - type: number
+              - type: string
+              - type: array
+              - type: object
+        require_approval:
+          oneOf:
+            - type: string
+              const: always
+            - type: string
+              const: never
+            - type: object
+              properties:
+                always:
+                  type: array
+                  items:
+                    type: string
+                never:
+                  type: array
+                  items:
+                    type: string
+              additionalProperties: false
+              title: ApprovalFilter
+          default: never
+        allowed_tools:
+          oneOf:
+            - type: array
+              items:
+                type: string
+            - type: object
+              properties:
+                tool_names:
+                  type: array
+                  items:
+                    type: string
+              additionalProperties: false
+              title: AllowedToolsFilter
+      additionalProperties: false
+      required:
+        - type
+        - server_label
+        - server_url
+        - require_approval
+      title: OpenAIResponseInputToolMCP
     OpenAIResponseInputToolWebSearch:
       type: object
       properties: