MCP Python SDK v2.3.0 released: primarily fixes, three new configuration options
v2.3.0
AI summary
MCP Python SDK released v2.3.0, primarily fixes with three new options. Tools with invalid x-mcp-header annotations now raise InvalidSignature at registration time; previously the server would start normally but the 2026-07-28 client would silently drop the tool. Empty _meta and params are no longer sent with requests, avoiding rejection by some servers. Added max_sse_event_size option (default remains 1 MiB per SSE event), MCPServer(subscriptions=False) can stop offering subscriptions/listen, and Client.call_tool re-lists tools and retries once after HeaderMismatch (-32020).