Title: lowlevel Server: widen on_* return types for InputRequiredResult; add subscriptions/listen slot by maxisbey · Pull Request #2967 · modelcontextprotocol/python-sdk · GitHub
Open Graph Title: lowlevel Server: widen on_* return types for InputRequiredResult; add subscriptions/listen slot by maxisbey · Pull Request #2967 · modelcontextprotocol/python-sdk
X Title: lowlevel Server: widen on_* return types for InputRequiredResult; add subscriptions/listen slot by maxisbey · Pull Request #2967 · modelcontextprotocol/python-sdk
Description: Type-only changes to the lowlevel Server constructor for the 2026-07-28 protocol revision. Changes Return-type widening — three on_* handlers can now return InputRequiredResult in addition to their concrete result type, matching MONOLITH_RESULTS in src/mcp/types/methods.py: on_call_tool → CallToolResult | InputRequiredResult on_get_prompt → GetPromptResult | InputRequiredResult on_read_resource → ReadResourceResult | InputRequiredResult These are the three methods whose request params extend InputResponseRequestParams. Widening is covariant, so existing handlers typed -> CallToolResult etc. still type-check unchanged. New dispatch slot — on_subscriptions_listen kwarg + _spec_requests row, so subscriptions/listen (the one new-in-2026 client→server request method) reaches a registered handler instead of METHOD_NOT_FOUND. InputRequiredResult validator — model_validator(mode="after") enforcing the spec's at-least-one-of input_requests / request_state requirement (matches the typescript-sdk and csharp-sdk behaviour). Not in this PR tasks/* — moved to the io.modelcontextprotocol/tasks extension; not core 2026-07-28. on_discover override — server/discover stays the auto-derived built-in. get_capabilities() — ServerCapabilities has no subscriptions field; nothing to set. Part of #2891. AI Disclaimer
Open Graph Description: Type-only changes to the lowlevel Server constructor for the 2026-07-28 protocol revision. Changes Return-type widening — three on_* handlers can now return InputRequiredResult in addition to their...
X Description: Type-only changes to the lowlevel Server constructor for the 2026-07-28 protocol revision. Changes Return-type widening — three on_* handlers can now return InputRequiredResult in addition to their...
Opengraph URL: https://github.com/modelcontextprotocol/python-sdk/pull/2967
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