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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Inconsistency in `types.py` schema for `RequestParams`","articleBody":"**Describe the bug**\n\nNot sure if I'm missing something, but I found that I was unable to add extra fields to `RequestParams` in the MCP Python schema in `types.py` (e.g., I'm trying to pass auth tokens along for `ListToolsRequest`). The Python MCP schema ignores extra fields at the top level of `RequestParams`, but the TypeScript MCP schema does not. \n\n**To Reproduce**\n\nTry to create a `RequestParams` instance with an extra field at the top level (not inside `meta`), e.g.:\n\n```python\nRequestParams(foo=\"bar\", meta=None)\n```\n\nThe additional field `foo` is ignored.\n\n**Expected behavior**\n\nExtra fields at the top level of `RequestParams` should be accepted, matching the TypeScript schema’s behavior.\n\n**Additional context**\n\n- The TypeScript interface allows arbitrary extra fields at the top level of params via:\n\n```ts\nexport interface Request {\n  method: string;\n  params?: {\n    _meta?: {\n      progressToken?: ProgressToken;\n    };\n    [key: string]: unknown;\n  };\n}\n```\n\n- The Python class only allows extra fields inside the `Meta` class:\n\n```python\nclass RequestParams(BaseModel):\n    class Meta(BaseModel):\n        progressToken: ProgressToken | None = None\n        model_config = ConfigDict(extra=\"allow\")\n    meta: Meta | None = Field(alias=\"_meta\", default=None)\n```\n","author":{"url":"https://github.com/lucasng32","@type":"Person","name":"lucasng32"},"datePublished":"2025-06-09T23:03:30.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/913/python-sdk/issues/913"}