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.

ChatGPT: no MCP servers or Connectors option in settings

When the Connectors or MCP section never appears: plan gating, Developer mode, app version, and workspace admin restrictions to check.

ChatGPT: adding an MCP server opens a blank page or will not connect

A blank authorize window or a connect that never finishes is usually the endpoint URL, blocked popups and cookies, or the server's OAuth setup.

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.

Cursor / VS Code: 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.

Perplexity: no option to add a custom MCP connector

Plan gating, the web-first settings location, workspace admin policy, and the manual client_id fix for servers without automatic registration.

Copilot Studio: cannot connect to your MCP server

The complete server URL, the Streamable HTTP requirement, public reachability, OAuth and Entra settings, and maker permissions, checked in order.

Stuck on something not listed here? Run the MCP Config Validator to catch JSON errors in your browser, or read the MCP server reference for endpoint, transport, and OAuth details.

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