Arbituro for coding agents

Arbituro is work management where every job says what finished means. This repository connects your coding agent to it: the MCP server's address, a plugin for each major harness, and four skills that teach an agent to work a job the way its done-when asks.

Your coding agent does the work and asks. The decision stays with a person.

What your agent can do

• Read the contract before writing. get_job gives the job in full: the description, the plan a person approved, and every done-when clause with who or what decides it.
• Work where the job says. The job names a branch. Commits that carry the job's key appear on the job as they are pushed, and the pull request links itself.
• Let CI decide what CI can. A clause "decided by the test check" is ticked by that check on the linked pull request, and by nothing else.
• Ask a person for the rest. claim_done records what the agent checked against a clause, and the person who decides it is asked in one press.
• File a document. Where a job asks for a document, a memo or a slide deck, file_result files it as Markdown.
• Leave a trail. Notes, proposals and new jobs are written under your name, and every call is on the record.

It cannot tick a clause, change one, finish a job, approve, merge, send, spend or delete. There is no tool for any of those. The full list is in docs/tools.md.

Install

You need an Arbituro workspace: sign up at app.arbituro.com. There is no key to make. Your agent opens a browser, you sign in, and it acts as you.

The server's address is https://app.arbituro.com/mcp.

Claude Code

claude plugin marketplace add writan-labs/arbituro-mcp

claude plugin install arbituro@writan-labs

The plugin adds the server and the skills. For the server alone:

claude mcp add --transport http arbituro https://app.arbituro.com/mcp

Codex

codex mcp add arbituro --url https://app.arbituro.com/mcp

codex mcp login arbituro

For the plugin, add this repository as a marketplace and install Arbituro from the Plugins directory:

codex plugin marketplace add writan-labs/arbituro-mcp

Gemini CLI

gemini extensions install https://github.com/writan-labs/arbituro-mcp

Cursor

Add the server to ~/.cursor/mcp.json, or to .cursor/mcp.json in a project:

{
  "mcpServers": {
    "arbituro": { "url": "https://app.arbituro.com/mcp" }
  }
}

This repository is also a Cursor plugin (.cursor-plugin/plugin.json), carrying the server and the skills together.

VS Code and GitHub Copilot

Add the server to .vscode/mcp.json:

{
  "servers": {
    "arbituro": { "type": "http", "url": "https://app.arbituro.com/mcp" }
  }
}

Everything else

Any client that speaks MCP over streamable HTTP with OAuth can connect to https://app.arbituro.com/mcp. docs/install.md has the configuration for Windsurf, OpenCode and others.

The skills, in any harness

The skills are plain Agent Skills and install into Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode and the rest with one command:

npx skills add writan-labs/arbituro-mcp

The skills

Skill	Use it to
arbituro-work-job	Work one job to its done-when: read it, branch, commit with its key, link the pull request, claim what you checked, leave a note.
arbituro-catch-up	See what is yours, what waits on you, and what happened in a project since you last looked.
arbituro-file-job	File work you found as a new job, after checking nobody already has.
arbituro-file-result	Write and file the document, memo or slide deck a job asks for.

Then say it the way the job page does:

Work ARB-12 in Arbituro.

One workspace, or all of yours

https://app.arbituro.com/mcp reaches every workspace you are in, and the project you name chooses the workspace. To give an agent one workspace and no other, connect that workspace's own address instead, which Settings → Keys and coding agent shows:

https://app.arbituro.com/mcp/<workspace>

Somebody in two clients' workspaces should connect each one separately, so what one client wrote never steers an agent working in the other's.

How sign-in works

• OAuth, in your browser. Your agent discovers the authorization server from the address, sends you to sign in, and keeps the token it is given. Arbituro has no personal access tokens for MCP.
• The agent is you. Everything it writes is under your name, and it can open only the projects you can.
• A token opens one door. A token for one address is refused at every other, and at the web app's own API.
• Every call is recorded, reads included, naming the client that made it.

More in docs/security.md. To report a vulnerability, see SECURITY.md.

For programs

The same operations are a JSON API at https://app.arbituro.com/api/v1, described by one OpenAPI document at /api/v1/openapi.json. It takes an API key made in your settings, for one workspace.

What is in this repository

Path	What it is
server.json	The server's entry for the MCP Registry
skills/	The four skills, shared by every plugin below
.claude-plugin/	The Claude Code plugin and its marketplace
.codex-plugin/, .agents/plugins/	The Codex plugin and its marketplace
.cursor-plugin/	The Cursor plugin
gemini-extension.json, GEMINI.md	The Gemini CLI extension
mcp/	The server's configuration in each harness's own format
snippets/AGENTS.md	A paragraph for your own repository's AGENTS.md
docs/	The tools, the install steps for every client, and how access works

The server itself is hosted by Arbituro and is not in this repository.

Licence

MIT. Arbituro is made by Writan Labs.