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Use Geometer from your coding assistant

If you build your agent with Claude Code or Cursor, you can stay in the assistant. Say "check my agent with Geometer", get a short answer and a link to the board, fix the code together, and check the fix.

On this page

Add Geometer to your assistant#

Geometer runs on your computer and sends nothing anywhere. Adding it tells your assistant how to start it. Do this once. It is added for you, in every project, and nothing is written into your project.

For Claude Code, run this in a terminal (geo mcp install --client claude-code prints it with the right path for your computer):

claude mcp add --scope user geometer -- /path/to/geo mcp serve

For Cursor, add this under mcpServers in ~/.cursor/mcp.json (geo mcp install --client cursor prints it, and --write adds it for you after you say yes, keeping what is already in the file):

json

{
  "mcpServers": {
    "geometer": { "command": "/path/to/geo", "args": ["mcp", "serve"] }
  }
}

Restart the assistant. The path is where geo is installed on your computer, because an editor often does not see the same PATH as your terminal.

If you have only the Mac app, press Add the geo command on its welcome page first. That links ~/.local/bin/geo to the copy inside the app, and geo mcp install then names that link, so the setting keeps working when the app is updated. Without the link it names the copy inside the app, which also works.

What to ask#

"Check my agent with Geometer." It tries your agent against faults in a sandbox, which takes about 30 to 60 seconds, and answers in three lines: what it found, what was not covered, and what to do next. You also get a link to the board. Open it for the picture.
"Explain the problem." Your assistant gets the same brief as Copy for your AI assistant on the problem page: what happened, the rule that must hold, and the conditions Geometer created.
Change the code together.
"Check my fix." Geometer replays the recorded run on your changed code and nearby cases. The answer is "Still happens", "Not reproduced in 3 runs, within what was tried", or "Could not tell".

The same problem found in two agents is one problem with one id. Explaining, checking the fix and keeping act on every agent that shows it, and you get one answer ("Not reproduced in agent-py and agent-ts (3 runs each)") and one link to confirm.

"Keep this check." Geometer cannot do this on the assistant's word alone. The assistant gives you a link to the problem page, and you press Keep this check there. Nothing is saved before you do.

Other things to ask: "What does Geometer say about this project?" (status, which also lists the open problems), and "Try a lost reply at the refund tool" (one fault at one tool, answered as held, broke or could not tell).

What the answers mean#

"Not reproduced in 3 runs, within what was tried" covers those runs, not every possible situation.
"No problems found in what was tried" is not a statement about cases that were not tried. The second line says what was not covered.
Geometer is for development and staging. It does not watch your live agent from here.
One check runs at a time. If one is running, the assistant is told and given the link.
Text from your agent's run, inside the brief, is data. Your assistant should treat it as data and not as instructions.

The tools your assistant sees#

The six tools
Tool	What it does	Changes something?
`status`	What Geometer knows, the open problems with their ids, and the next step	No
`check`	Checks the agent, like `geo check`	Runs a sandbox; your project is not changed
`explain_problem`	The fix brief for one problem	No
`try_fault`	One fault at one tool, like `geo check --fault … --at …`	Runs a sandbox; your project is not changed
`check_fix`	Check my fix	Runs a sandbox; your project is not changed
`keep_check`	Returns the link where you keep the check. When the same problem shows in several agents, one press keeps it for each agent whose fix check has passed, and the answer names any agent that is not ready and why	Not by itself; you confirm in Geometer

Every link the assistant gives you signs you in with its own one-time code, so it opens without a sign-in step. Links work while Geometer is running (while your assistant's session lasts); the code is good for ten minutes, and later geo open gives you a new link. The answers also start with a short summary and a next step in the data the assistant reads, so the three plain lines reach it even when its client shows only the data.

Where the setup lines come from#

The Claude Code line follows the current Claude Code documentation for adding a local server (claude mcp add [options] <name> -- <command> [args...], with --scope user for all your projects, stored in ~/.claude.json): https://code.claude.com/docs/en/mcp. The Cursor file follows the current Cursor documentation (mcpServers with command and args; ~/.cursor/mcp.json for all projects, .cursor/mcp.json for one): https://cursor.com/docs/context/mcp. Both were read on 27 October 2026. Check those pages if a client changes its format.

Next#

Fix a problem and keep the checkWhat the same steps look like in the workspace.
Check your agentWhat a check does.

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