MCP
MCP (Model Context Protocol) lets Captain Who connect to external tool services. User-configured MCP servers currently support only stdio processes launched on the local device. HTTP, OAuth, and remote MCP URLs are not available.
Before you begin
Obtain the following from the MCP server publisher:
- The exact location of the local executable.
- Startup arguments in the required order.
- A valid working directory.
- Installation instructions and security provenance for the program.
The current configuration does not provide fields for environment variables, dedicated secrets, or request headers. Do not place tokens, passwords, or cookies in command arguments or the working directory. These fields are stored and displayed as ordinary local configuration.
Add a server
- Open “Settings → MCP.”
- Select “Add server” under “External.”
- Enter a name.
- Use the file picker to select the executable.
- Put each startup argument on a separate argument row in the order required by the publisher.
- Select a working directory.
- Decide whether to enable “Allow tools to run automatically.” When off, every call asks for approval. When on, identity and risk checks still apply.
- Select “Save.”
A newly saved server is disabled by default and does not start immediately.
Authorize launch and enable
- Open the server details from the list.
- Enable the server.
- The first enablement shows the launch information for review. Confirm that this starts the specified process on your device.
- After authorization, Captain Who connects to the server and discovers its tools.
- When the status changes to “Ready,” inspect the tool catalog.
If you later change the executable, arguments, or working directory, the old connection stops and the launch authorization becomes invalid. Review the configuration again the next time you enable it. Replacing the executable or related code may also require reauthorization.
Use it in a task
After enablement, MCP tools become dynamic tools available to the agent. You can name the server you expect the agent to use, for example:
Use the enabled “Read-only database tools” server to query records added this week. Return a summary only and do not write data.
“Ask every time” displays an approval card with a summary of the server, tool, and arguments. “Allow tools to run automatically” can reduce approvals for routine calls, but it does not bypass checks on server identity, the tool catalog, arguments, concurrency, or sensitive risks.
Once a call may have been sent to the external process, a timeout, cancellation, or disconnection may produce “Unknown outcome.” Do not automatically repeat writes, messages, payments, or similar actions. Check the external system first.
Manage and troubleshoot
The details page shows connection status, tool count, startup configuration, and optional technical details. Common states include:
- Starting/Connecting/Discovering tools: Wait for negotiation to complete.
- Ready: The complete tool catalog is available.
- Degraded/Needs attention: The catalog is incomplete or the state is abnormal. Do not assume an absent tool does not exist.
- Error/Waiting to reconnect: Check the program, arguments, and working directory, then select “Retry connection.”
Only a complete, validated tool catalog is provided to the agent. Refreshing the catalog does not repair an error in the server itself.
Disabling a server prevents new calls and closes the connection. Deleting it removes only the Captain Who configuration; it does not uninstall the local program. The final outcome of active calls may still be unknown.
Built-in MCP and external servers
The “Built-in” area under “Settings → MCP” currently includes browser automation. It is managed by the app, does not require an executable or arguments, and is not part of your external-server list. See Browser Automation for usage.
Current limitations
- External servers support local stdio only.
- MCP Resources, Prompts, Sampling, Elicitation, Tasks, and Apps are not part of the agent user path. The current user path primarily uses Tools.
- No environment-variable fields, dedicated secret fields, OAuth, or remote-connection configuration.
- On Windows, an external server cannot be treated as having complete process-tree isolation.
- Names, descriptions, and “read-only” labels supplied by a server are untrusted hints and cannot lower approval requirements on their own.