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safe-fix-mcp

Pythonリポジトリ内のデッドコードを検出し、自動削除しても実際に安全な唯一の種類の検出結果(単一の名前だけをインポートする行の未使用インポート)についてブランチ + PRを提案する、実際のMCPサーバーです。それ以外に検出されるもの(未使用の関数、クラス、未使用の依存関係)はレポートのみに留まります。マージは常に人間が行います。このツール自体が何かをマージすることは決してありません。

なぜこれが存在するのか

ほとんどの「デッドコード」ツールはレポートを出すだけで終わります。さらに踏み込むツールは、通常は安全策なしに削除します。これはどちらでもありません。削除後にターゲットリポジトリ自身の完全なテストスイートが実際に通ることを条件に、実際の、最小限の、レビュー可能なPRのドラフトを作成します。ヒューリスティックではなく、実際のpytestの実行です。スイートが失敗した場合は、何もコミットもプッシュもされず、リポジトリは開始時とまったく同じ状態のままになります。

Related MCP server: Python Code Guardian MCP Server

ツール

scan_dead_code(repo_path=".", min_confidence=60)

読み取り専用です。vulture(デッドコード)とdeptry(依存関係の問題)を実行し、人間が読める形式の検出結果リストを返します。何も変更しません。

propose_removal_pr(repo_path=".")

  • 作業ツリーが汚れている場合は拒否します。未コミットの作業の上で編集することは決してありません。

  • 単一の名前だけをインポートする行のうち、vultureの信頼度が90%以上の未使用インポートのみに絞り込みます(from x import y, zはスキップされます。行全体を削除するとzも黙って削除されてしまうためです)。

  • 実際のブランチを作成し、条件に合うインポートを削除し、リポジトリの実際の完全なテストスイートを実行します。

  • 実際に成功した場合のみ、コミット、プッシュ、そしてgh pr createによるPRのオープンを試みます。

  • ghがインストールされていない、または認証されていない場合でも、ブランチは実際にコミット・プッシュされます。低下するのはPR作成だけであり、実際のエラーが返されるため、手動でPRを開くことができます。

インストール

pip install -e .

MCPクライアントの設定に追加します(例: Claude Code):

claude mcp add safe-fix-mcp -- safe-fix-mcp

または、ローカルテスト用に直接実行します:

python -m safe_fix_mcp.server

要件

  • Python ≥ 3.10

  • PATHにgitがあること

  • propose_removal_prで実際にPRを開きたい場合は、PATHにgh(GitHub CLI)があり、認証済みであること — これがない場合でも、ブランチは実際にプッシュされ、ツールが手動でPRを開くように指示します。

開発

pip install -e ".[dev]"
pytest

既知の制限

vultureはscan_dead_code/propose_removal_pr自体を「未使用」とフラグ付けします。これは既知の誤検知の一種であり、実際のバグではありません。これらは実行時に@mcp.tool()デコレータによってディスパッチされ、ソース内のどこからも直接呼び出されないため、静的コールグラフ解析では実際の呼び出し元(MCPフレームワーク自体)を確認できないのです。

実際に検証する

scripts/verify_real_client.pyは、パッケージ化されたサーバーを実際のサブプロセスとして起動し、実際のmcp.client.ClientSessionを使って通信します。これは実際のMCPクライアントが使用するのと同じ経路です。変更後のスモークテストとして役立ちます:

python scripts/verify_real_client.py

Available Tools

2 tools
propose_removal_prA

Propose a real branch+PR removing only unused imports (single-name import lines, >= 90% vulture confidence) from a Python repository. Runs the repo's own full test suite as a safety gate before ever committing or pushing — a failure there reverts everything and nothing is committed or pushed. If gh isn't available or PR creation otherwise fails, the branch is still committed and pushed for real; only the PR itself needs opening manually. A human always merges — this never merges anything itself.

repo_path: path to a real git repository with a clean working tree (uncommitted changes are refused, not overwritten).

ParametersJSON Schema
NameRequiredDescriptionDefault
repo_pathNo.

Output Schema

ParametersJSON Schema
NameRequiredDescription
resultYes

TDQS

A4.5/5.0
Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description fully carries the behavioral burden, and it does so well. It explains that the test suite is a safety gate, that failures revert all changes, that branch commits/pushes persist if only PR creation fails, and that human merge is always required.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is somewhat long but every sentence earns its place, covering prerequisites, side effects, failure modes, and parameter meaning. The critical safety guarantees are front-loaded, and there is no filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a tool with one optional parameter and an output schema, the description is remarkably complete. It covers prerequisites, refused inputs, failure behavior, push semantics, and merge policy, so an agent has enough to call it correctly without additional context.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, but the description compensates by explaining repo_path as a real git repository with a clean working tree and noting uncommitted changes are refused. This adds meaningful semantics beyond the bare schema field, though it does not mention optionality/default behavior beyond what the schema already shows.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool's specific action: propose a real branch and PR that removes unused imports from a Python repository. It adds precise scoping (single-name import lines, >=90% vulture confidence) that makes its purpose concrete and distinct from a general cleanup tool.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies usage context by specifying criteria for eligible imports and requiring a clean git repository with a full test suite. However, it never explicitly addresses when to use this tool versus scan_dead_code or mentions exclusions, leaving the routing partially to inference.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

scan_dead_codeA

Scan a Python repository for real dead code (vulture) and dependency issues (deptry). Read-only — never modifies anything. Returns a human-readable list of findings, or "No real candidates found."

repo_path: path to the repository to scan (must contain a pyproject.toml for the dependency checks to run; dead-code scanning works regardless). min_confidence: vulture's own confidence threshold (0-100). Lower values surface more candidates but more false positives.

ParametersJSON Schema
NameRequiredDescriptionDefault
repo_pathNo.
min_confidenceNo

Output Schema

ParametersJSON Schema
NameRequiredDescription
resultYes

TDQS

A4.6/5.0
Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations present, the description carries full burden and does so well: it states the tool is read-only, never modifies anything, and describes the exact output (human-readable findings or 'No real candidates found.'). It also discloses the pyproject.toml dependency for deptry and explains the confidence threshold's trade-off. No annotation contradiction.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is compact—three sentences for behavior plus two parameter explanations—and all content earns its place, with read-only status front-loaded.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a two-parameter tool with an output schema and a single sibling, this description covers input semantics, prerequisites, behavioral safety, and result format. The only omitted piece is explicit sibling differentiation, which belongs to usage guidelines. Combined with schema and output schema, an agent has everything needed to invoke it correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters5/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema has 0% description coverage, and the description fills in all of it: repo_path is the path to the repository and must contain pyproject.toml for dependency checks, and min_confidence maps to vulture's 0-100 threshold with a false-positive trade-off. This goes well beyond the parameter names and defaults.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description opens with a specific verb-resource pair: scan a Python repository, and names the two tools (vulture, deptry) and the two classes of findings (dead code, dependency issues). This clearly distinguishes it from the sibling propose_removal_pr, whose action is proposing a PR, not scanning.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

No explicit guidance on when to use this tool versus propose_removal_pr, nor any when-not conditions. However, the read-only declaration and human-readable output imply this is an analysis step, and the requirement about pyproject.toml provides some context. This makes usage predictable but not explicitly ruled for alternatives.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Tool Schema Changelog

Recent tool additions, removals, and schema changes observed during successful MCP inspections.

  1. 2 tool updatesv0.1.2
    • First observedpropose_removal_pr
    • First observedscan_dead_code

TDQS

A4.4/5.0

Scored across 2 tools

Disambiguation5/5

scan_dead_code is purely read-only analysis, while propose_removal_pr actually creates a branch and PR. Their purposes are complementary and unlikely to be confused.

Naming Consistency4/5

Both tool names use lower_snake verb-first conventions: scan_dead_code and propose_removal_pr. The pattern is predictable, though the second name is slightly less clean because 'removal_pr' bundles an action and an object into one noun phrase.

Tool Count3/5

Two tools is on the thin side and sits at the borderline of feeling complete. However, each tool has a distinct role in a focused analyze-then-propose workflow, so the small count is plausible for a narrow server.

Completeness3/5

The scan surfaces both dead code and dependency issues, but propose_removal_pr only handles unused imports. Dependency fixes and non-import dead-code removals are therefore dead ends, creating a notable gap in the advertised safe-fix domain.

Maintenance

ActivitySlowing
ResponsivenessNo issues

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