MCP and judge-cli for agents

crates/agent exposes the pipeline to other programs in two transports over one set of operations. judge-mcp is an MCP server on stdio. judge-cli has one subcommand per operation and prints JSON. judge-api --mcp also serves the same MCP tools over HTTP at /mcp, for agents that are not on the host. It needs an MCP_TOKEN too, and the flag without a token is refused at startup.

Pipeline and sessions

judge runs the built-in pipeline: extraction and synthesis on the configured models, citation validation, one retry. It spends model budget under the process’s JUDGE_MAX_USD and, over /mcp, counts against MCP_JUDGE_LIMIT.

Sessions turn the pipeline inside out. The agent asks for a session, receives the extraction prompt and answers it itself. It then receives the synthesis prompt, rendered from the same retrieved context the bot would use. It may ask for one round of extra rules. Then it submits a verdict, which is admitted only through the same citation validation, with the same rejection notice and one retry. The judge makes no model call, because the agent is the model. This is how Claude Code answers rules questions in this repository (the judge skill under .claude/skills/), and how a reported bad answer is reproduced for free.

judge-cli begin "does bob's trigger count goyf's mana value as 0?"   # → session id + extraction prompt
judge-cli extract <session> extraction.json                          # the agent's extraction → synthesis prompt
judge-cli rules <session> 202.3 702.19                               # optional, once
judge-cli verdict <session> verdict.json --persist                   # validated, or a rejection to correct

Session-persisted calls are thread history only. Nothing can rate them, so the prior-call leg never shows them as examples. Session thread ids carry an agent: prefix that a Discord thread id cannot have, so a session cannot read a channel’s history.

Lookups

card <name>, card-info <uuid>, get-rules <id>..., search <query> [--limit N] and glossary <term> query the database directly and cost nothing. config prints the resolved provider and model setup with secrets redacted. about prints the source offer: the repository holding this instance’s source, the commit it was built from, the licence and copyright. Over MCP the same offer is the tail of the server’s initialization instructions and the about tool, so a client sees it before calling anything.

Connecting an MCP client

Locally, .mcp.json in the repository starts target/release/judge-mcp for Claude Code (cargo build --release -p judge-agent first). Remotely:

claude mcp add --transport http judge https://judge.example.com/mcp \
  --header "Authorization: Bearer <MCP_TOKEN>"

MCP_ALLOWED_HOSTS must name the public hostname, and the token must be at least 24 printable ASCII bytes. The deployment runbook covers the rest.