MCP Setup

Configure MCP servers to give the assistant access to any external tool or service that publishes an MCP endpoint.

DO NOT run exploratory commands. Do not check available CLI commands, search for bun/npx/node, or investigate transport types. Follow the steps below exactly and stop when done. (Looking up a service's MCP endpoint URL in its own documentation is allowed when the service is not in the recipe table, per Step 3.)

When to Use

USE THIS SKILL WHEN:

• User asks to connect any external tool or service via MCP
• User asks "what MCP servers / integrations do I have?"
• An MCP tool returns an auth error → run assistant mcp auth <name>
• User wants to disconnect an integration

Prefer Native OAuth Integration (check this first)

Many services have built-in OAuth integrations that are simpler and more reliable than MCP. Before setting up MCP, check whether the service already has a native OAuth provider:

assistant oauth providers list

If the service appears in that list, connect it natively instead of using MCP:

assistant oauth connect <provider>

Only use MCP when:

• The service is not in assistant oauth providers list
• The user explicitly asks to use MCP for a specific service
• The native OAuth integration fails or lacks features the user needs

Step 1 — Detect your environment

Before doing anything else, determine which environment you are in.

Try host_bash:

echo "desktop ok"

• If it succeeds → you are on the desktop app. Use host_bash for all commands, including auth (opens a local browser).
• If it is unavailable → you are on the web app (or a cloud-hosted session). Use bash for all commands, including auth (the platform handles the browser redirect).

Both environments fully support MCP. The only difference is which tool runs the commands.

Step 2 — Check the recipe table

Check this table before doing anything else. If the service is listed, run the command shown and do nothing else — no exploration, no checking available commands, no looking up documentation.

If the service is not in this table, go to Step 3.

Step 3 — Unknown service

Find the MCP endpoint URL in the service's documentation, then run:

assistant mcp add <name> -t streamable-http -u <url>

Then run assistant mcp list. If it shows ! Needs authentication, run assistant mcp auth <name>.

• On desktop → run via host_bash (opens the local browser).
• On web app → run via bash (the platform handles the browser redirect).

Reference: All Commands

Run list, add, remove, and reload via bash on both environments. Run auth via host_bash on desktop, or via bash on the web app.

List servers

assistant mcp list
assistant mcp list --json   # machine-readable output

Shows each server's connection status, transport, and URL/command. Status indicators:

• ✓ Connected
• ✗ Error
• ! Needs authentication

Add a server

assistant mcp add <name> -t <transport> -u <url>

Transport types:

• streamable-http — most modern remote servers (use this by default)
• sse — legacy remote servers
• stdio — local process: use -c <command> and -a <args...> instead of -u

Examples:

assistant mcp add linear -t streamable-http -u https://mcp.linear.app/mcp
assistant mcp add context7 -t streamable-http -u https://mcp.context7.com/mcp
assistant mcp add local-db -t stdio -c npx -a -y @my/mcp-server

Authenticate (OAuth)

assistant mcp auth <name>

• On desktop → run via host_bash (opens the user's local browser for OAuth login).
• On web app → run via bash (the platform handles the browser redirect and saves tokens).

Tokens are saved automatically. Use when:

• assistant mcp list shows ! Needs authentication
• An MCP tool call fails with an auth/token error
• Setting up a new OAuth-protected server for the first time

Remove a server

assistant mcp remove <name>

Removes config and cleans up stored OAuth credentials.

Reload

assistant mcp reload

Manually signals the assistant to reconnect all MCP servers from disk. Normally not needed — the assistant detects changes automatically after add, remove, and auth. Use this only if a server's tools aren't appearing after ~10 seconds.

Advanced Configuration

mcp add covers the common cases. For stdio environment variables, edit $VELLUM_WORKSPACE_DIR/mcp.json under mcpServers.<name>.env. Auth headers for remote servers go through assistant mcp add -H or the settings UI, not mcp.json.

SKILL COMPLETE WHEN

Match the completion condition to the task:

• Add / authenticate: the server appears in assistant mcp list with status ✓ Connected and the user confirms its tools are available in the conversation.
• List: the current servers (or the fact that none are configured) have been reported to the user.
• Remove / disconnect: assistant mcp remove <name> succeeds and the server no longer appears in assistant mcp list.