Connect

The Fuse MCP server lets AI assistants operate your Fuse account directly: search for prospects, manage lists and campaigns, triage your inbox, pull analytics, and more — all through natural language. It implements the Model Context Protocol, so it works with Claude, ChatGPT, Grok, Cursor, Claude Code, Codex and any other MCP-capable client. It is a separate surface from the REST API. The REST API is for your own code and authenticates with API keys; the MCP server is for AI assistants and authenticates by signing in to your Fuse account — no API key involved.

Server URL

https://mcp.fuseai.com

The same URL is shown in the Fuse app under Settings → MCP, with a copy button, shortcuts to the connector settings of Claude, ChatGPT and Grok, and a setup prompt you can paste into any other assistant to have it install the server for you.

Connections set up with the earlier URL, https://mcp.tryfuse.ai, keep working. There is no need to reconnect them.

How authentication works

The server uses standard OAuth, which every major MCP client handles for you:

The first time your assistant connects, it registers itself with Fuse automatically and opens a browser window.
You sign in the way you sign in to Fuse, with your email and password or with Google or Microsoft, and approve the connection. You need an existing Fuse account with a verified email address; the sign-in page doesn’t create one.
The assistant receives its own tokens and refreshes them silently from then on.

There is nothing to configure and no key to paste. Any member of a team can connect, whatever their role. The connection acts as you: tools run with your user’s permissions and see exactly the data your account sees. A connection that goes unused for about a month expires, and the client will ask you to sign in again.

A connected assistant can do what you can do in Fuse — including sending emails and modifying lists and campaigns — whenever you ask it to. Only connect clients you trust, and disconnect the server from the client’s settings when you no longer use it. Removing the server deletes the client’s tokens. Fuse can’t revoke a connection from its side, and the last access token stays valid for up to an hour.

Set up your client

In Claude’s web or desktop app, go to Settings → Connectors, choose Add custom connector, name it Fuse, paste https://mcp.fuseai.com as the URL and continue with the default sign-in settings. Then click Connect and sign in with your Fuse account.On Claude’s Team and Enterprise plans an owner adds the connector first, under the organization’s Connectors settings; members then find it in their own connector list and click Connect.

claude mcp add --transport http fuse https://mcp.fuseai.com

Then run /mcp inside a session and pick fuse to complete the sign-in, or run claude mcp login fuse.

Add the server to ~/.cursor/mcp.json (or your project’s .cursor/mcp.json):

{
  "mcpServers": {
    "fuse": {
      "url": "https://mcp.fuseai.com"
    }
  }
}

Cursor opens the sign-in flow the first time it connects.

codex mcp add fuse --url https://mcp.fuseai.com
codex mcp login fuse

The second command opens the browser for the sign-in; Codex may offer it on its own right after the first.

Custom connectors need ChatGPT’s Developer mode, which not every plan offers and which some plans limit to reading. Turn it on in ChatGPT’s settings (under Connectors → Advanced, or Security and login, depending on your plan), then go to Settings → Connectors, create a custom connector named Fuse with https://mcp.fuseai.com as the URL, and sign in when prompted.

Go to grok.com/connectors, click New Connector, pick Custom, enter https://mcp.fuseai.com and sign in when prompted.

Point the client at https://mcp.fuseai.com. Any client that supports the Streamable HTTP transport and OAuth works; everything it needs is discoverable from the URL. If the client can read a setup prompt, the one under Settings → MCP in the Fuse app walks it through the whole setup.

Once connected, the client lists the Fuse tools automatically — see Tools & limits for what they can do. The list is long, so check Client limits if some tools seem to be missing.

For custom clients

Protocol and discovery details

Everything a hand-rolled client needs is served from the standard discovery endpoints:

GET https://mcp.fuseai.com/.well-known/oauth-protected-resource names the authorization server.
GET https://core.backend.fuseai.com/.well-known/oauth-authorization-server lists the registration, authorization, and token endpoints.

The OAuth flow is authorization code with PKCE (S256) for public clients (token_endpoint_auth_methods_supported: ["none"]), with dynamic client registration and the single scope mcp:tools. Send scope=mcp:tools on the authorization request; it is required, and the WWW-Authenticate challenge does not carry it. Access tokens last one hour; refresh tokens rotate on every refresh and last 30 days from their last use.The transport is stateless Streamable HTTP:

Send JSON-RPC messages with POST. Batches (arrays of messages) are accepted.
There is no server-push stream: GET is not served (it answers 404), and the Mcp-Session-Id the server returns on initialize doesn’t need to be sent back.
Supported protocol versions: 2025-11-25, 2025-06-18, 2025-03-26, and 2024-11-05. A client that asks for a version the server doesn’t know is answered with 2025-11-25.
Each POST is one request against the rate limits, whether it carries one message or a batch.

Unauthenticated requests receive 401 with a WWW-Authenticate header pointing at the resource metadata, which is the standard signal for clients to start the OAuth flow.

Troubleshooting

Symptom	Likely cause	Fix
Client reports `401` (`MISSING_TOKEN`, `INVALID_TOKEN` or `INVALID_TOKEN_TYPE`)	The connection’s tokens expired or were invalidated	Disconnect and reconnect the server in your client to sign in again
Client reports `429` (`RATE_LIMIT_EXCEEDED`)	You hit the per-user rate limits, which all your connected clients share	Wait a minute and retry. The 5,000-a-day limit resets 24 hours after the first request of that day’s window
Sign-in page rejects you	The consent screen takes your Fuse email and password, or Google or Microsoft sign-in; an unverified email address, a deleted account, an address with no Fuse account, or a Google or Microsoft identity other than the one linked to your account is refused	Sign in the way you sign in to the Fuse app, verify your email address first if you haven’t, or reset your password in the app, then retry
Tools don’t appear after connecting	The client cached an older tool list	Refresh or reconnect the server in the client
Calls fail with “FuseAI replaced this tool on October 6, 2026…”	The client still lists the tools from before October 2026, such as `prospect_search` or `campaigns`	Open the Fuse connector in your client’s settings and choose Refresh, since reconnecting alone may not reload the list. If that doesn’t help, remove Fuse and add it again to load the current tools
Some Fuse tools are missing	The client caps the tools it passes to its model across all its servers, or part of Fuse was briefly unavailable when the list was built	Turn off tools or servers you don’t need in the client’s settings, then refresh or reconnect; if it persists, retry a minute later
Calls fail with “Insufficient FuseAI credits”	Every tool call needs a balance of at least 100 credits	Add credits in the Fuse app, then retry

Still stuck? Write to support@fuseai.com with the client you’re using and roughly when the failure happened.

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MCP server

Server URL

How authentication works

Set up your client

For custom clients

Troubleshooting

​Server URL

​How authentication works

​Set up your client

​For custom clients

​Troubleshooting

Server URL

How authentication works

Set up your client

For custom clients

Troubleshooting