Summary
The diagram updates while the agent is still explaining it.
The output is not a file that lands in the repository - it is a canvas in the browser that changes as services, databases and connections are added. That makes it useful during the conversation where a design is being decided, not only for documenting one afterwards.
What it is
A hosted MCP server for Composer, a visual system design tool. The agent creates and works on diagrams through the server, and the canvas at usecomposer.com updates in real time as it does.
What you get
- A new diagram created from what the agent describes - services, databases, queues and the connections between them
- Your existing diagrams listed
- A diagram selected as the one being worked on
- A diagram renamed
- A live canvas that changes while the agent works, rather than a file to open afterwards
Requirements
A Composer account - connect over HTTP and your browser opens for authorization the first time. Nothing to install on the HTTP path; an npm package covers clients that need stdio.
Setup effort
One command — claude mcp add --transport http composer https://mcp.usecomposer.com