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Title: Add support for Elicitation by ihrpr · Pull Request #625 · modelcontextprotocol/python-sdk · GitHub

Open Graph Title: Add support for Elicitation by ihrpr · Pull Request #625 · modelcontextprotocol/python-sdk

X Title: Add support for Elicitation by ihrpr · Pull Request #625 · modelcontextprotocol/python-sdk

Description: Elicitation Spec PR Overview Adding support for the elicitation feature, allowing servers to interactively request additional information from clients during tool execution. The implementation follows a layered approach with both low-level protocol support and a high-level API through FastMCP. Key Changes 1. Protocol Layer (src/mcp/types.py) Added ElicitRequest, ElicitRequestParams, and ElicitResult types to support the elicitation protocol Extended ServerRequest and ClientResult to handle elicitation messages Follows the MCP specification for elicitation support 2. Low-Level Server/Client (src/mcp/server/session.py, src/mcp/client/session.py) Added elicit() method to ServerSession for sending elicitation requests Added elicit() method to ClientSession for handling server elicitation requests Design decision: Uses raw dictionaries instead of Pydantic models - this maintains consistency with the low-level API design which provides direct protocol access without data modeling abstractions 3. FastMCP High-Level API (src/mcp/server/fastmcp/server.py) Added Context.elicit() method that returns an ElicitationResult object Design decision: Returns a result object instead of raising exceptions for decline/cancel actions. This treats user declining or cancelling as expected outcomes rather than error conditions Enforces MCP specification requirement that elicitation schemas only contain primitive types (str, int, float, bool) Validates schemas at runtime with descriptive error messages FastMCP Interface Design The FastMCP elicitation interface prioritizes type safety and explicit result handling: @server.tool() async def book_table(date: str, party_size: int, ctx: Context) -> str: class ConfirmBooking(BaseModel): confirm: bool = Field(description="Confirm booking?") notes: str = Field(default="", description="Special requests") result = await ctx.elicit( message=f"Confirm booking for {party_size} on {date}?", schema=ConfirmBooking ) if result.action == "accept" and result.data: # result.data is typed as ConfirmBooking if result.data.confirm: return f"Booked! Notes: {result.data.notes}" elif result.action == "decline": return "User declined" else: # cancel return "User cancelled" Interface characteristics: result.data is typed according to the provided schema All three user actions (accept/decline/cancel) are handled explicitly Validation errors are captured in result.validation_error when user input doesn't match schema Schema validation happens before sending the request, failing fast if non-primitive types are used

Open Graph Description: Elicitation Spec PR Overview Adding support for the elicitation feature, allowing servers to interactively request additional information from clients during tool execution. The implementation foll...

X Description: Elicitation Spec PR Overview Adding support for the elicitation feature, allowing servers to interactively request additional information from clients during tool execution. The implementation foll...

Opengraph URL: https://github.com/modelcontextprotocol/python-sdk/pull/625

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