Custom MCPs

A custom MCP connects Ren to a service outside the Marketplace. MCP is a protocol that gives agents access to tools. For example, an internal documentation server can provide search tools to projects that use it.

Use an app when one exists, since apps include skills and a tested setup. Otherwise, connect a remote MCP server or run a local server on the space’s machine.

The API resource is mcp. CLI commands use ren mcps.

Add a custom MCP

A custom MCP is one of two kinds:

• Remote: a server reached over HTTP or SSE at a URL, like https://mcp.example.com.
• Local: a command that runs on the space’s machine, like npx -y @modelcontextprotocol/server-github.

For a remote server, choose how it authenticates:

Authentication	What you connect
None (no credential)	Nothing. Use this for public servers.
OAuth	A signed-in account, through the provider’s sign-in page
API key (bearer)	A token Ren sends in a header
Basic	A username and password
Custom headers or query parameters	Values Ren places in the headers or URL you define

Web app Ask Ren CLI

Instruction method Web appAsk RenCLI

1. Open Marketplace → Custom MCPs and select Add custom MCP.
2. Choose where to add it: your organization, or a project. Choosing a project also adds the custom MCP to it.
3. Pick a Transport: Remote or Local.
4. For Remote, enter the Server URL. Choose an Authentication type. For Local, enter the Command. Add any required Arguments and Environment variables.
5. Enter a Name, then select Add MCP.

If the URL is already registered, Ren shows an error with Add second account. Select it only when you mean to reach the same server with a different account.

Add our docs MCP server at https://mcp.acme.dev as a custom MCP and add it to this project. It uses OAuth.

Open in Ren

ren mcps create --name "Acme docs" --type remote --mcp-server-url https://mcp.acme.dev --auth oauth

Run ren mcps create --help for local commands and other authentication types.

Connect its credentials

If the server needs a credential, connect it before Ren uses the server. Ren saves it in the project’s space, like an app connection. See Credentials.

Web app Ask Ren CLI

Instruction method Web appAsk RenCLI

1. Add the custom MCP to a project, or ask Ren to use it in a chat.
2. When Ren asks, select Connect and sign in, or enter the key, password, or fields the server needs.
3. Select Continue. The connection shows as connected.

Connect the Acme docs MCP.

Open in Ren

Finish signing in or enter the key on the card Ren shows.

For OAuth:

ren credentials connect <mcp> --vault-id <vault-id>

For a token, pipe it to ren credentials create <vault-id> --auth-type bearer --mcp-id <mcp-id> --token-stdin.

Add it to a project

Web app Ask Ren CLI

Instruction method Web appAsk RenCLI

1. Open Marketplace → Custom MCPs and select the custom MCP.
2. Select Add, choose a project, and select Add.

The drawer lists the server’s tools and the credentials it needs.

Add the Acme docs custom MCP to the Support project.

Open in Ren

ren projects mcps add <project-id> --mcp-id <mcp-id>

To detach a custom MCP, select its trash icon in the composer’s Connect menu. You can also run ren projects mcps remove or ask Ren. Detaching it doesn’t delete its definition.

Who can see a custom MCP

A custom MCP added at the organization level is visible to every member. One added to a project in your personal space is private to you. A credential is never part of a custom MCP’s definition, so sharing the definition doesn’t share your account.

Publish with ren mcps publish <mcp-id> or mcp_publish. Everyone can see the published definition, without authentication settings or credentials. Publishing is permanent, but you can deprecate it with ren mcps deprecate.