Urbit MCP

A general-purpose Model Context Protocol interface for Urbit.

Developer Setup

1. Build and Install

• Requires a running Urbit ship, real or fake, running on a machine you have terminal access to.
• Requires peru package manager. Install and set that up if you don't have it already. Make sure peru --version works.

Create and mount the desk on your Urbit ship:

> |new-desk %mcp
> |mount %mcp

In the urbit-mcp folder, run the build script. By default this will install dependencies into /dist in this folder. Use the -p argument to additionally copy the %mcp source and its dependencies into your ship's desk. This script will take a minute if it's your first time running it.

$ cd urbit-mcp
$ build.sh -p ~/path/to/zod/mcp

> |commit %mcp
> |install our %mcp

2. Authentication Setup

Get your ship's web login code from the Dojo:

> +code
lidlut-tabwed-pillex-ridrup
~zod:dojo>

Authenticate and get session cookie:

curl -i http://localhost:80/~/login -X POST -d "password=lidlut-tabwed-pillex-ridrup"

Extract the cookie from the set-cookie header, which will look like this:

urbauth-~your-ship=0v3.j2062.1prp1.qne4e.goq3h.ksudm

3a. Register with Codex

Simply add this to your ~/.codex/config.toml:

[mcp_servers.zod]
enabled = true
url = "http://localhost:80/mcp"
http_headers = { "Cookie" = "urbauth-~your-ship=0v3.j2062.1prp1.qne4e.goq3h.ksudm" }

3b. Register with Claude Code

Add the MCP server to Claude using HTTP transport:

claude mcp add --transport http zod http://localhost:80/mcp --header "Cookie: urbauth-~your-ship=0v3.j2062.1prp1.qne4e.goq3h.ksudm" --scope user

Usage

Tools

Just ask! You can see the default tools here.

You can ask your LLM to add new Tools. Give it a description (and ideally, examples) and it will do its best, or provide a Hoon thread for it to adapt to run in %mcp-server. Threads in %mcp-server must be of signature $-((map @t argument:tool:mcp) shed:khan).

Prompts (slash commands)

Depending on your agent harness, MCP prompts for most default tools may be available as slash commands, e.g. /mcp__zod__<tool name>.

Running these will append a prompt snippet to the conversation and call out to the LLM provider. You can ask your LLM to add new Prompts.

Resources (@ mentions)

Depending on your agent harness, MCP resources may be referenced with an @ mention to pull their contents into the context window.

@zod:https://docs.urbit.org/llms.txt

You can ask your LLM to add new Resources by providing an https:// URI to a public webpage or a beam:// URI to a file in your Urbit's Clay filesystem.

Contributing

This repo requires commits to be signed with a Groundwire identity. PRs with unsigned commits will be rejected by CI.

Setup commit signing

You need an Urbit ship running the %vitriol agent.

Quick install:

./hooks/install.sh <your-ship-url>/vitriol "<auth-cookie>"

Manual install:

git config gpg.program /path/to/hooks/groundwire-sign
git config commit.gpgsign true
git config groundwire.sign-endpoint <your-ship-url>/vitriol
git config groundwire.sign-token "<auth-cookie>"

Once configured, all commits will be automatically signed with your ship's Ed25519 networking key. The CI verifies signatures against on-chain keys via vitriol.bot.

Re-signing existing commits

If you have unsigned commits on a branch:

git rebase --exec "true" HEAD~N

(where N is the number of commits to re-sign)

Development

Build Commands

• ./build.sh - Build full desk
• ./build.sh build-dev - Build dependencies
• ./build.sh clean - Clean build directories
• ./build.sh -p /path/to/desk - Build and copy to a ship's desk