{"version":"2.1.277","anchor":"mcp-tool-use-id-now-sourced-from-the-tool-use-record-when-av","canonical_anchor":"mcp-tool-use-id-now-sourced-from-the-tool-use-record-when-av","heading":"MCP tool-use id now sourced from the tool-use record when available","tier":"internal","area":"MCP","scope":null,"heads_up":null,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.277\/e\/mcp-tool-use-id-now-sourced-from-the-tool-use-record-when-av","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.277","markdown":"### MCP tool-use id now sourced from the tool-use record when available\n\nMCP tool calls now reuse an existing tool-use id instead of deriving one, and add a per-request header\n\n**What**\n\nWhen Claude Code makes an MCP (Model Context Protocol) tool call, it now prefers to use the tool-use id already attached to the call record, rather than deriving one from request headers as it did before. It also now adds a new per-request metadata header carrying the request id, in addition to the existing `claudecode\/toolUseId` metadata.\n\n**Why**\n\nThis is an internal correctness and traceability improvement for how MCP tool calls are identified, which can help with matching requests to responses correctly and debugging.\n\n- Area: MCP\n- Tier: Under the hood\n- Useful: 1\/5\n- Signal: 1\/5"}