MCPServer as a thin composition of the 2026 helpers #2897

MCPServer composes the public helpers from the feature issues (MRTR, caching hints, HTTP headers, subscriptions/listen — and the existing schema-inference / registry helpers) into the high-level decorator API — thin, not a monolith with private machinery. Someone using lowlevel Server should be able to reach for the same building blocks.

What's in it

• Compose the public helpers: tool/resource/prompt registries, schema inference, cache hints, x-mcp-header annotations, MRTR signaling, listen publishing — exposed via @server.tool() / @resource() / @prompt() kwargs and ctx verbs.
• Design needed: how MCPServer presents MRTR and subscriptions/listen given the stateless/distributed nature of 2026 — there's no per-connection state to lean on and servers may be horizontally scaled (e.g. where does requestState live between rounds; how do listen publishers reach a stream that might be on another instance).
• Keep MCPServer itself thin: anything it does should be a public helper a lowlevel-Server user could call directly.

Conformance

• (SDK API surface — proven via in-repo / interaction tests)

Dependencies

• Depends on: Context object (layered, per-request) #2895
• Depends on: MRTR (multi-round-trip requests) #2898
• Depends on: Caching hints (ttlMs / cacheScope) #2899
• Depends on: HTTP standard headers + x-mcp-header #2900
• Depends on: subscriptions/listen #2901

References

• python-sdk MCPServer