"Couldn't reach the MCP server" in Claude: a checklist
Claude says "Couldn't reach the MCP server" but your server runs. Check in order: URL, inbound requests, transport, OAuth, IP allowlist.
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Why claude.ai can't connect to your local MCP server (and how to fix it)
claude.ai rejects localhost MCP URLs because Anthropic's servers make the call, not your browser. Why that happens and what a working fix needs.