Claude custom connector not working? A troubleshooting checklist

Start by finding where it fails

A custom connector can fail at four points: you cannot add it, it will not connect, sign-in fails, or it connects but Claude does not use its tools. Each has different causes, so first note exactly where it stops and what message you see. Then work through the matching section below.

You cannot find the option to add a custom connector

On individual Pro and Max plans, Anthropic's steps are Customize, then Connectors, then the add button and Add custom connector. On Team and Enterprise plans, members do not add custom connectors there. Anthropic documents that only Owners and Primary Owners can add them on Team plans, and on Enterprise plans Owners, Primary Owners, and people with a custom role that includes Manage access to Libraries. Owners add them under Organization settings, then Connectors, then Add, Custom, and Web.

If you are a member, ask an owner to add the connector for the organization. Once it is added, you will find it under Customize, then Connectors, usually with a Custom label, and click Connect. Also check your plan: Anthropic says custom connectors are available on Free, Pro, Max, Team, and Enterprise, with Free limited to one, so a Free account that already has one cannot add another.

It will not connect, even though the URL works for you

This is the most common cause of confusion. Anthropic's documentation states that Claude connects to a remote MCP server from Anthropic's cloud infrastructure rather than from your device, and that this applies to claude.ai, Claude Desktop, Cowork, and the mobile apps. A server on a private corporate network, behind a VPN, or blocked by a firewall will not connect, even if you can open it from your own machine.

• Make sure the server has a public HTTPS address with a valid certificate.
• If it must stay on a private network, allowlist Anthropic's published IP ranges in your firewall.
• Use the full MCP endpoint path the server expects, often ending in /mcp.
• Confirm the server speaks a remote transport. Local servers configured in claude_desktop_config.json are a separate mechanism and are not available in claude.ai or Cowork.
• Check the server's logs for the request. If nothing arrives, the problem is the network path, not Claude.

Sign-in or OAuth errors

When adding a connector, Claude detects authentication settings and lets you change them. Under Authentication you choose Sign in now, Sign in when needed, or No sign in. Under OAuth client you choose Claude's published identity, automatic registration, or your own OAuth client. Under Request headers you can add a fixed credential such as an API key if the server does not use OAuth.

A mismatch here is the usual cause of sign-in failures. If the server expects OAuth but you chose No sign in, requests are rejected. If your authorization server does not support automatic registration, choose your own OAuth client and enter its details. If it uses an API key, put the key in Request headers instead.

On the server side, the MCP authorization specification requires servers to validate that access tokens were issued for them. A token issued for a different audience should be rejected, which is correct behavior, so make sure your identity provider issues tokens for the MCP server's own address. Note also that Anthropic says editing a custom connector means removing it and adding it again with the new details.

Connected, but the tools do not show or are not used

Connectors are enabled per conversation. Anthropic's steps are the plus button at the lower left of the chat, then Connectors, where each connector has a toggle. Within a connector, tools can also be disabled from the Search and tools menu. Check both before debugging the server.

• Confirm the server returns its tools when listed. The MCP Inspector tool can list and call them directly.
• Check that tool names and descriptions are clear. Claude chooses tools from their descriptions, and vague ones get skipped.
• On Team and Enterprise, owners can disable specific tool calls that render interactive connectors in Organization settings, so check whether a tool was turned off there.
• In Research, Anthropic notes that advanced research cannot invoke tools from local MCP servers, and that Claude may call connector tools many times without further approval.

A quick test sequence

When you cannot tell which layer is failing, test from the outside in. Each step rules out one cause, so you stop guessing and know which person needs to fix it.

• From a machine outside your network, open the server URL. If it does not respond, fix the network path or allowlist first.
• Connect with the MCP Inspector and list the tools. If that fails, the server or transport is the problem, not Claude.
• Call one tool from the Inspector with a valid token. If it fails, check token validation and the audience your identity provider issues.
• Add the connector in Claude with the matching authentication settings, then connect as a regular member, not only as an owner.
• Enable it in a new conversation and ask a question that clearly needs one tool. If Claude does not call it, rewrite that tool's description.
• Keep a short log of each fix. Most teams hit the same two or three problems again when they add their next connector.

When to get help

If the network path is open, authentication settings match, and the server still returns errors, the problem is in the server code: transport handling, token validation, or tool schemas. That is where Prestyj's custom Claude connector work usually starts when a team brings us a connector that almost works. We fix the server, then test it in each Claude client your team uses.