> For the complete documentation index, see [llms.txt](https://docs.fritesai.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.fritesai.com/reference/mcp-tools.md).

# 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](/product/mcp-worktree-mode.md).

## `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):

```bash
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:

```toml
[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](/reference/cli.md).

## See also

* [MCP worktree mode](/product/mcp-worktree-mode.md). The product overview of this mode.
* [CLI](/reference/cli.md). The standalone `frites run` equivalent.
* [Configuration](/reference/configuration.md). Synthesis and oracle keys that shape a run.