MCP fixes
The configuration errors and silent failures that show up the first time you wire an MCP server into an AI client. Each page is a focused, copy-paste fix.
Quick answer
Most MCP failures are one of a handful of errors: the server connects but no tools show, the connection drops after a minute (an SSE timeout), OAuth loops without finishing, or the config file is silently invalid. Match your symptom to one of the pages below, covering Cursor, Claude, ChatGPT, and Copilot.
Cursor: bearer token or 401 from a remote MCP server
How to pass a bearer token in your Cursor mcp.json and what to check when the server returns 401. Prefer OAuth where the server supports it.
Claude Desktop: MCP tools do not appear after restart
Where the config file lives, why npx needs -y, and the log lines that show the real error.
ChatGPT: custom MCP connector returns no tools
Plan gating, dev mode, and the per-chat toggle to check when ChatGPT cannot see the server.
Claude Code: MCP OAuth loops or never finishes
Transport flag, callback port, and the claude mcp list checks for a stuck OAuth handshake.
VS Code with Copilot: wrong root key in mcp.json
servers vs mcpServers, the right file location, and how Copilot Chat surfaces MCP tools.
MCP: SSE timeout or unexpected disconnect
Why long-lived SSE connections drop, when to switch to Streamable HTTP, and what to check on a proxy.
VS Code / Cursor: Failed to acquire MessagePort (createMcpProcessChannelConnectionResult)
Why every MCP server fails to start even though it runs fine in a terminal, and the reload, update, and Windows antivirus fixes for the editor's IPC handshake bug.
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