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MCP servers

Adding a custom MCP server

Connect your agent to any app that offers an MCP server, even if it is not in the list.

The app icons on the Capabilities page are only a few of the apps you can connect. Many other apps offer an MCP server, and you can add any of them yourself as long as you know its address.

What you need

Look in the app's documentation for its MCP server. You need two things:

  • The server URL, usually something like https://mcp.example.com/mcp. Your agent runs online, so it needs a server that is reachable over the internet. Servers that you are asked to install and run on your own computer will not work.
  • How to sign in. The documentation will usually say whether you sign in with your account (OAuth), or with an API key or token.

Add the server

Open your agent, go to Capabilities, scroll down to MCP servers and click Add an MCP server.

  1. Enter a name for the server. This is the name you will use with !enable-mcp and !disable-mcp, so we recommend keeping it short, for example Linear.
  2. Enter the server URL.
  3. Choose how to sign in:
    • OAuth if the app lets you sign in with your account. After you click Add, click Connect on the new card and sign in.
    • API key if the app gives you a key or token. Enter the header name and value from the app's documentation. Most apps use Authorization as the name and Bearer followed by your key as the value.
    • None if the server does not need you to sign in.
  4. Click Add.

Once your agent is connected, the card shows how many tools the server has. We recommend clicking Select recommended straight away. See Must read: Managing costs and MCP tools.

If it does not connect

  • Check the URL for typos, and make sure it is the MCP server's address, not the app's website.
  • If OAuth fails, the app may not support the kind of sign-in Salts uses. Check whether the app offers an API key instead, and use API key.
  • If the app asks you for a redirect URL, use the one shown at the bottom of the MCP servers section.
  • After fixing anything, click Refresh tools on the card.
  • If the card shows Last failed tool call, the message under it says what went wrong.