Claude Custom Connector MCP: Setup and Authentication

To add a Claude custom connector for MCP, go to Customize → Connectors → Add custom connector, name it, paste the server's HTTPS URL and pick an authentication mode. For an MCPifex server, paste the gateway URL with your API key at the end and choose "No sign-in". No OAuth setup is needed.

Add MCPifex as a custom connector

Say you've already created a PostgreSQL instance in the MCPifex portal and generated an API key. In claude.ai:

1. Open Customize → Connectors → Add custom connector. For an organization, have an owner add the Web connector through Organization settings → Connectors first.
2. Name the connector something recognizable, like "MCPifex."
3. For the server URL, paste https://mcpifex.com/mcp/<YOUR_MCPX_KEY>, with your real key in place of the placeholder.
4. Pick "No sign-in" and leave Request headers and OAuth fields blank. The key is already in the URL.
5. Click Add, then enable the connector through the conversation plus menu. Check the tools it found and ask for one harmless read, then look at the actual tool result.

Treat that URL like a password. Anyone who has it can call every tool enabled on that key. If it leaks, revoke the key in the portal, and enable only the tools a conversation needs.

Where the menu lives

On Free, Pro and Max, go to Customize → Connectors, then the "+" button, then "Add custom connector."

On Team and Enterprise, only organization Owners can add a connector for everyone: Organization settings → Connectors → Add → Custom. Choose "Web" if it asks for a type. Members then open their own Customize → Connectors and click "Connect" on the entry the Owner added. Either way, use the "+" button inside a chat to turn the connector on for that conversation.

As of September 2026, Anthropic is rolling out a two-step dialog, with name and URL first and then auto-detected authentication settings. Some organizations still see the older single-screen version with the same fields.

Which authentication mode?

The dialog offers three modes:

• Sign in now: runs the server's OAuth flow for every user before they can use it.
• Sign in when needed: connects immediately and asks for sign-in only when a tool call needs it.
• No sign-in: anyone with the connector URL can use it as configured. This is the mode for a fixed credential such as an API key.

An optional Request headers section can carry an API key, but it's in beta and limited to some organizations. If your dialog doesn't show it, use the URL-key form above. If it does, type the scheme out: Bearer your-token, not just your-token, or the server rejects the request.

That's why MCPifex accepts two forms of the same API key: an Authorization: Bearer mcpx_... header, or the key as the first path segment (https://mcpifex.com/mcp/mcpx_...) for clients that can't send headers.

Custom connector or directory connector?

They use the same mechanism: a remote MCP server reachable over HTTPS. Anthropic's Connectors Directory adds a review label and a browsing page. A custom connector is the same connection built by hand from a URL you already have.

Test the endpoint before you add it

Before you paste the URL into claude.ai, confirm the gateway answers from your machine. The quickstart has a curl script that runs initialize and tools/list against it. It only proves your machine can reach the gateway with that key. The connector needs its own check, so ask Claude for a named read operation once it's added.

Transport: Streamable HTTP, not SSE

Claude's Advanced settings choose the transport from the URL. A URL ending in /sse selects the older SSE transport, and anything else uses Streamable HTTP. The MCPifex URL doesn't end in /sse, so leave the setting on its default.

MCPifex's gateway uses the handshake-based MCP transport. Clients on the current revision interoperate through the spec's backward-compatibility rules.

If it doesn't work

• "Server unreachable": Claude connects from Anthropic's cloud, not your device, so the server must be reachable on the public internet. A server behind a VPN or only listening locally fails even if it works for you. Check the exact URL.
• 401 error: the key is wrong or was revoked. If you use the header form, include the full Bearer prefix.
• Instance disabled or Google connection revoked: these need a different fix. The troubleshooting reference lists gateway errors.
• Custom connector limit: Free accounts get one. Anthropic doesn't state a fixed cap for Pro, Max, Team or Enterprise.

Read the reported error before assuming it's a network problem.

Common questions

Can I use an Authorization header instead of putting the key in the URL?

If your organization has the request-headers beta, yes. Use "No sign-in", the base URL https://mcpifex.com/mcp, and an Authorization header of Bearer followed by your key. Otherwise use the path-key URL.

Does the URL need to end in /sse?

No. MCPifex uses Streamable HTTP at https://mcpifex.com/mcp/<YOUR_MCPX_KEY>. Adding /sse would change the endpoint.

About MCPifex

MCPifex hosts MCP servers so you don't install anything. The same instance and key work in Claude on the web and in Claude Desktop, so see connect an MCP server to Claude Desktop for the desktop steps. A free account covers 3 instances, and the pricing page has the details. New to the protocol? Read about the Model Context Protocol.