{"version":"2.1.311","anchor":"mcp-tool-list-scan-skipped-unless-a-tool-schema-mentions-x-m","canonical_anchor":"mcp-tool-list-scan-skipped-unless-a-tool-schema-mentions-x-m","heading":"MCP servers that don't use x-mcp-header skip an extra tool check","tier":"internal","area":"MCP","scope":"individual","heads_up":false,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.311\/e\/mcp-tool-list-scan-skipped-unless-a-tool-schema-mentions-x-m","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.311","markdown":"### MCP servers that don't use x-mcp-header skip an extra tool check\n\nClaude Code now skips a per-tool check on MCP servers unless one of their tools mentions x-mcp-header\n\n**What**\n\nMCP servers are outside tools Claude Code connects to, and each describes the tools it offers. Claude Code used to run a check on every tool's description. It now first looks for `x-mcp-header`, an extension, anywhere in the server's tool list. If it is not there, the check is skipped.\n\n**Why**\n\nMost MCP servers don't use that extension, so they no longer go through work that was not needed.\n\n- Area: MCP\n- Tier: Under the hood\n- Useful: 1\/5\n- Signal: 2\/5\n- Scope: individual\n- Heads-up: no"}