Connect a local MCP Server

Goal

Connect a trusted local MCP Server to Captain Who, verify that its tool catalog is available, and complete one controlled call in a conversation.

Before you begin

Get the exact executable, arguments, and working directory from the MCP Server's official documentation.
Install the program and its dependencies in a terminal according to the provider's instructions. Captain Who's add-server page does not install them for you.
User-configured MCP Servers currently support local stdio only. HTTP, Streamable HTTP, and OAuth integrations are not yet available.
Do not put tokens, passwords, or cookies in command arguments, the working directory, or the server name. The current management interface does not provide custom environment-variable or request-header configuration either.

Steps

1. Add the server

Open Settings → MCP and select Add server in the External section. Enter:

Name: a recognizable local name;
Executable: select the actual program with the system picker;
Arguments: enter each argument in the exact order required;
Working directory: select the directory the server needs at runtime;
Tool-call policy: for a first connection, choose Ask every time.

Save the configuration. Saving a server does not automatically grant permission to start it or call its tools.

2. Review and authorize startup

When you enable the server, Captain Who shows the local program, arguments, and related entry points it will start. Review every item before confirming. If you later replace the executable, code entry point, or configuration, the previous startup authorization may become invalid and require another review.

Startup authorization means “allow this exact configuration to start.” It does not mean the process is sandboxed, nor does it allow all of its tools to run automatically.

3. Wait for the server to become ready

The status normally progresses through Starting and Discovering tools before reaching Ready. Open the server details and load the tool catalog. Confirm that the catalog is complete and contains the tools you expect.

If the catalog is marked Partial, Stale, or Failed, it is not treated as a complete callable catalog. Refresh or repair the server before proceeding; do not continue based on an incomplete list.

4. Test it in a conversation

Create a low-risk task. Specify the objective without assuming a tool name, for example:

text

Review the MCP tools currently available and use the “Local Knowledge Base” server to find read-only information about the release process. First explain which tool you plan to call and why. Do not perform any write operations.

When the approval card appears, verify the server, tool, rationale, and parameter structure before approving or rejecting the call. Tool names, descriptions, and “read-only” labels supplied by an MCP Server are third-party claims and are not sufficient security evidence on their own.

Expected result

The server details show Ready, the tool catalog is complete, and the conversation timeline shows an MCP call from the correct server with either a successful result or an explicit failure.

Troubleshooting

Startup authorization required: Reopen the details, verify the current executable, arguments, and working directory, then authorize startup.
Startup fails or repeatedly reconnects: First verify the program locally using its provider documentation. Check argument order and the working directory.
No tools appear: Distinguish between “complete but empty” and “catalog incomplete.” The latter requires refreshing or repairing the connection.
Approval parameters are unavailable: Some unfinished approvals cannot resume after a restart. Cancel the request and initiate a new, explicit call.
Call result is unknown: The request might already have reached the MCP Server. Check the external system before repeating any write operation.
A secret is required: Do not put it in the arguments. Because the current management interface does not support environment variables or SecretRef, servers that depend on this type of secret injection cannot be configured safely. Use a server that does not require this configuration method.

For the conceptual distinction, see Skill and MCP. For more support boundaries, see Capability limits.