> ## Documentation Index
> Fetch the complete documentation index at: https://docs.fuseai.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Connect

> Connect Claude, ChatGPT, Cursor, Codex or any MCP client to Fuse and drive your account through natural language.

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](https://modelcontextprotocol.io), 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](/authentication); the MCP server is for AI assistants and authenticates by signing in to your Fuse account — no API key involved.

## Server URL

```text theme={null}
https://mcp.fuseai.com
```

<Info>
  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.
</Info>

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:

1. The first time your assistant connects, it registers itself with Fuse automatically and opens a browser window.
2. 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.
3. 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.

<Warning>
  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.
</Warning>

## Set up your client

<Tabs>
  <Tab title="Claude">
    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**.
  </Tab>

  <Tab title="Claude Code">
    ```bash theme={null}
    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`.
  </Tab>

  <Tab title="Cursor">
    Add the server to `~/.cursor/mcp.json` (or your project's `.cursor/mcp.json`):

    ```json theme={null}
    {
      "mcpServers": {
        "fuse": {
          "url": "https://mcp.fuseai.com"
        }
      }
    }
    ```

    Cursor opens the sign-in flow the first time it connects.
  </Tab>

  <Tab title="Codex">
    ```bash theme={null}
    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.
  </Tab>

  <Tab title="ChatGPT">
    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.
  </Tab>

  <Tab title="Grok">
    Go to [grok.com/connectors](https://grok.com/connectors), click **New Connector**, pick **Custom**, enter `https://mcp.fuseai.com` and sign in when prompted.
  </Tab>

  <Tab title="Any other client">
    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.
  </Tab>
</Tabs>

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

## For custom clients

<Accordion title="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](/mcp/tools#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.
</Accordion>

## 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](/mcp/tools#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](/mcp/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](mailto:support@fuseai.com) with the client you're using and roughly when the failure happened.


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