SEP-2243: HTTP Header Standardization for Streamable HTTP Transport

Description

Per SEP-2243 (HTTP Standard Headers), MCP clients MUST send the following HTTP headers on POST requests:

• Mcp-Method: Set to the JSON-RPC method value from the request body (REQUIRED on every POST)
• Mcp-Name: Set from params.name (for tools/call, prompts/get) or params.uri (for resources/read, resources/subscribe, resources/unsubscribe) when present

Context

The cxxmcp (C++ SDK) conformance testing revealed that the official conformance test suite's reference client (TypeScript SDK) does not send these headers, making the conformance suite self-contradictory. See:

• typescript-sdk#2176 — TypeScript SDK bug report
• conformance#323 — Conformance suite self-contradiction
• typescript-sdk#2178 — Fix PR for TypeScript SDK

Impact

Servers that enforce SEP-2243 (reject missing Mcp-Method with HTTP 400) are incompatible with clients that don't send these headers. This affects cross-SDK interoperability.

Request

Please implement Mcp-Method and Mcp-Name header support per SEP-2243 to ensure cross-SDK compatibility.

从 Java SDK 的 streamable HTTP transport client 入手，跟踪 POST 请求的构建方式。使用 SEP-2243 和此处描述的请求体字段来确定标头值；完成的标准是适用的 POST 请求发送 Mcp-Method 和 Mcp-Name，使执行该标准的服务器能够接受它们。