Custom MCP connectors

The Model Context Protocol (MCP) is an open standard for connecting AI apps to outside tools. An MCP server offers tools, such as searching a database or reading files, that any app speaking MCP can call.

So anything that speaks MCP can become a connector, from a vendor's hosted server to a script on your own machine. Its tools then work in Agent mode chats, next to the sources on your canvas. Ready-made connectors are covered in Connectors.

Note: Only add servers you trust. A connector's tools can read, change or send data, and whatever a chat passes to a tool goes to that server.

Add a remote server

1. Open Settings > Connectors and click Add.
2. In Add a custom connector, enter a unique Name and the server's URL, for example https://mcp.example.com/mcp.
3. If the server takes an API key, click Add header and enter it, for example Authorization with Bearer YOUR_KEY.
4. Click Add.

While the button reads Checking, Slashspace connects and lists the server's tools. It tries the Streamable HTTP transport, then SSE, and remembers whichever answers.

If the check fails, Could not connect shows why. Fix it and try again, or click Save anyway. Chats only use a connector once a check passes.

Sign in with OAuth

If the server uses browser sign-in, a Connect your account card appears. Click Sign in, approve access in your browser within two minutes, and return to Slashspace, which saves and checks the connector. Or click Save for later and use the Sign in button on its row when you're ready.

Your browser hands the sign-in back to Slashspace through a local address (127.0.0.1). Tokens refresh on their own after that.

Tip: Leave Headers empty for a server that uses sign-in. With headers present, Slashspace treats them as your credentials and doesn't offer sign-in.

Add a server that runs on this computer

Switch on Runs on this computer and fill in Command, Arguments, one per line, and Environment (click Add variable for each variable the server needs, such as an API key).

For example, the reference filesystem server (it needs Node.js), limited to one folder: set Command to npx and the arguments to:

-y
@modelcontextprotocol/server-filesystem
/Users/you/Documents

On Windows, set Command to cmd and add /c and npx as the first two argument lines.

Clicking Add runs the command right away to check it. Later, Slashspace starts it when a chat needs it and stops it after about 30 minutes unused.

The command runs with your user account's permissions: it can reach anything you can, so scope it narrowly. It inherits only basics such as PATH and HOME, so add every variable it needs under Environment.

Edit, turn off or remove

On the connector's row in Your connections:

• The switch hides its tools from every chat without deleting it.
• ⋯ > Edit: saved header values stay hidden, so leave one blank to keep it. A renamed header needs its value again, and a new URL needs a new sign-in. To change between remote and local, remove and re-add.
• ⋯ > Check connection reconnects and refreshes the tool list.
• ⋯ > Remove deletes it, with its saved headers and sign-in, after you confirm.

An amber warning with Reconnect means the last check or chat use failed; the reason shows beside it.

Connectors are saved in mcp.json under ~/Library/Application Support/Slashspace/config/ on macOS, or %APPDATA%\Slashspace\config\ on Windows. Header values and sign-in tokens go in a separate file, encrypted with your system's secure storage. Environment values for local servers stay in mcp.json as plain text.

Add to Slashspace links

Server authors can publish an Add to Slashspace link. Opening one launches Slashspace with Add a custom connector prefilled with a name and HTTPS URL (never keys or local commands); you review it and click Add. To make one, see Add to Slashspace button.

Troubleshooting

• "Timed out after 15 seconds": check the URL. A first npx run downloads the package and can outlast the check, so run the command once in a terminal, then try again.
• ENOENT: Slashspace can't find the program. Use its full path (which npx in Terminal prints it), or the cmd form on Windows.
• 401 with headers: the key is wrong or expired. Edit and retype it.
• Sign-in fails: start again from Slashspace rather than reusing an old browser tab. "Encrypted storage is required to sign in to a connector" means your system has no secure storage.
• Stops mid-chat: the chat warns it is unavailable and skips it until a check passes. Fix the cause, then click Reconnect (or Sign in, if its sign-in expired).
• Logs: Help > Open Log Folder (⌘⇧L, or Ctrl+Shift+L on Windows and Linux) opens the folder with Slashspace's log, which records each failed check. A local server's own errors aren't captured there; run its command in a terminal to see them.

More help: Troubleshooting and support.