MCP tools

The MCP worktree mode (@frites/mcp) exposes two tools over an stdio MCP transport: frites_implement runs a council of full agents in isolated git worktrees and returns one vetted diff plus a comparison, and frites_apply lands a chosen diff onto a fresh branch. The server is named frites. For how the mode fits together, see MCP worktree mode.

frites_implement

Dispatches a coding task to multiple full agents (claude/codex) in isolated git worktrees, filters them with the repo's tests, and returns one vetted diff plus a comparison. It is long-running (minutes). Review the result, then call frites_apply.

Argument	Type	Required	Meaning
task	string	yes	What to implement or fix.
repoPath	string	yes	Absolute path to the target git repository.
n	integer 1–5	no	Number of agents.
agents	string	no	Comma list of agent kinds, e.g. claude,codex. A token starting with codex maps to codex-cli, one starting with claude maps to claude-cli.
acceptanceCriteria	string	no	Acceptance criteria for the agents and oracle.
baseRef	string	no	Git ref to branch from (default HEAD).

The tool returns a Markdown result (formatResultText) containing the run id, decision, rationale, the recommended candidate, a per-agent comparison table (kind, status, files, Δlines, tokens in→out, oracle pass/fail), a synthesis status line, and the cost note. Synthesized candidates are marked with a ⚗︎ glyph. It also returns structured content (toStructured) and one resource_link per candidate diff, persisted under .frites/runs/<runId>/<agentId>.diff (with result.json alongside) in the target repo. On error it returns an isError result with the failure message.

frites_apply

Applies a diff from a previous frites_implement run onto a fresh branch frites/<runId>. It applies the recommended candidate by default, or a specific one via candidateId. It requires a clean working tree and never pushes.

Argument	Type	Required	Meaning
runId	string	yes	The run id from a previous frites_implement call.
repoPath	string	yes	Absolute path to the target git repository.
candidateId	string	no	Apply this candidate's diff instead of the recommended one (e.g. a tighter passing child instead of a synthesized result).

Apply behavior:

• If candidateId is given but no candidate with that id exists in the run, the tool returns an error listing the available candidate ids.

• If the chosen candidate has no diff to apply, it returns an error.

• On success it applies the diff to a new branch frites/<runId> and returns the branch name plus structured { branch, runId, candidateId }. The result tells you to review and commit; frites never auto-merges or pushes.

Registration

Claude Code

Register once for Claude Code (available in every repo):

claude mcp add --scope user frites -- pnpm --dir ~/nodejs/frites mcp

Codex

Register once for Codex in ~/.codex/config.toml. The 60-second default tool timeout must be raised: tool_timeout_sec = 600 is required because frites_implement runs for minutes:

[mcp_servers.frites]
command = "pnpm"
args = ["--dir", "/Users/whatl3y/nodejs/frites", "mcp"]
tool_timeout_sec = 600

Progress and result-size behavior

• Progress. When the MCP client supplies a progressToken, frites_implement streams notifications/progress updates as the engine emits events (agents starting/finishing, oracle results, synthesis, reconciliation), each with a human-readable message and an incrementing step count. Without a progress token, no notifications are sent.

• Result size. Full candidate diffs are written to disk under .frites/runs/<runId>/ and surfaced as resource_link entries rather than inlined, keeping the returned text result compact. Per-candidate token counts are rendered compactly (e.g. 11.2k) in the comparison table.

• Lifecycle. The server self-terminates when its MCP client disconnects (stdin EOF, termination signals, or being reparented to PID 1), so it never lingers as an orphan.

Typical flow

In a session: "use frites to implement X" → review the diff → "use frites_apply with runId …" (optionally candidateId=<agent> to land a specific candidate). The same flow is available from the terminal via frites "implement X" --repo … --apply / --apply-candidate <id>. See the CLI.

See also

• MCP worktree mode. The product overview of this mode.

• CLI. The standalone frites run equivalent.

• Configuration. Synthesis and oracle keys that shape a run.