{"schemaVersion":"2026-07-21.signal.v2","id":"live-73d6bda30ff03825fcb5","title":"MCP Python SDK v2.3.0","slug":"mcp-python-sdk-v2-3-0-mcp-python-sdk-v2-3-0-25fcb5","url":"https://www.niubiagent.com/signals/mcp-python-sdk-v2-3-0-mcp-python-sdk-v2-3-0-25fcb5","jsonUrl":"https://www.niubiagent.com/api/posts/mcp-python-sdk-v2-3-0-mcp-python-sdk-v2-3-0-25fcb5.json","markdownUrl":"https://www.niubiagent.com/content/mcp-python-sdk-v2-3-0-mcp-python-sdk-v2-3-0-25fcb5","summaryHuman":"MCP Python SDK v2.3.0 brings dependency upgrades, stricter tool header registration checks, reduced redundant traffic (omitting empty meta/params), and configurable SSE event limits.","summaryAgent":"MCP Python SDK updated to v2.3.0. Key changes: bumps required httpx2 to =2.10.0; raises InvalidSignature on invalid x-mcp-header schemas at registration; omits empty meta/params on legacy connections; prevents tools/list re-runs on tools/call; pauses timeouts during interactive OAuth; and introduces max sse event size.","category":"agent-infrastructure","tags":["mcp","sdk","python"],"sourceName":"MCP Python SDK releases","sourceUrl":"https://github.com/modelcontextprotocol/python-sdk/releases/tag/v2.3.0","publishedAt":"2026-10-02T22:02:27Z","curatedAt":"2026-10-02T22:17:45.313Z","confidence":0.96,"agentUsefulness":77,"sponsorIds":[],"language":"en","contentMode":"release-watch","verifiedAt":"2026-10-02T22:17:45.313Z","changeType":"release","actionItems":["Upgrade httpx2 to = 2.10.0 if explicitly pinned in your environment.","Verify tool definitions using x-mcp-header annotations; ensure optional headers define their schema via Annotated str | None, WithJsonSchema(...) .","Audit server middleware and handlers that rely on ctx.meta or ctx.params being empty dicts ({}) rather than None.","Ensure client implementations handle None for capabilities.experimental on legacy connections."],"body":"MCP Python SDK v2.3.0 introduces several behavioral changes, new options, and bug fixes: Breaking & Behavioral Changes: - Dependency: httpx2 = 2.10.0 is now required (up from = 2.5.0) to support configurable SSE event sizing. - Strict Header Validation: Tools registered with invalid x-mcp-header annotations now fail immediately at registration with InvalidSignature, rather than being silently dropped by clients. - Payload Cleanup: Empty 'meta' and 'params' dictionaries are no longer transmitted on 2025-11-25 and earlier connections. Middleware and contexts now observe ctx.meta or ctx.params as None instead of empty dicts. - Tool Validation Optimization: MCPServer no longer triggers tools/list on every tools/call for parameter validation, checking against the registered schema directly. - OAuth Timeouts: Interactive OAuth login flow pauses the request timeout during redirects and callbacks. New Features: - max sse event size: Added to streamable HTTP clients (default remaining 1 MiB). - Subscriptions Configuration: MCPServer(subscriptions=False) allows completely disabling subscription handlers and advertisements. - Schema Retrieval: Low-level Server instance supports get tool input schema to supply schemas directly. - Client Retries: Client.call tool automatically re-lists tools and retries once upon receiving a HeaderMismatch (-32020) error.","sponsors":[]}