ruff-check
Runs ruff check and returns structured lint diagnostics (file, line, code, message).
This record as markdown: /tools/io-github-dave-london-pare-python/ruff-check.md
What ruff-check does on Python
AI agents invoke ruff-check to trigger actions in Python. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call: builds kicked off, notifications sent, workflows started.
| Parameter | Type | Required | Description |
|---|---|---|---|
fix | boolean | — | Auto-fix problems |
diff | boolean | — | Show diff of fixes without applying (--diff) |
path | string | — | Project root path |
config | string | — | Path to custom ruff config file |
ignore | array | — | Rule codes or prefixes to suppress (e.g. ['E501']) |
select | array | — | Rule codes or prefixes to enable (e.g. ['E', 'F401']) |
compact | boolean | — | Prefer compact output |
exclude | array | — | File patterns to exclude from checking |
noCache | boolean | — | Disable cache (--no-cache) |
preview | boolean | — | Enable preview rules (--preview) |
targets | array | — | Files or directories to check (default: ['.']) |
lineLength | integer | — | Override the configured line length (--line-length) |
Parameters from the server's own tool schema.
Why ruff-check is rated High
The tool executes the ruff linter against code/files. While ruff check is read-only in intent (it only checks, not fixes), it runs an external process whose scope depends on arguments. It could scan arbitrary files or directories. Classified as Execute due to running an external command, with medium severity since it does not modify or delete data.
From the tool's definition Runs ruff check and returns structured lint diagnostics
Risk signalsAccepts file system path (path) · High parameter count (16 properties)
Attacks that exploit this kind of access
The rule that runs ruff-check safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Python, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For ruff-check, this is the rule to start with:
ruff-check stays usable, but rate-capped: a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect Python, apply this rule, and every ruff-check call is checked against it from then on.
Questions about ruff-check
Runs ruff check and returns structured lint diagnostics (file, line, code, message). It is categorised as a Execute tool in the Python MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
ruff-check accepts 12 parameters: fix, diff, path, config, ignore, select, compact, exclude, noCache, preview, targets, lineLength. The full parameter table on this page comes from the server's own tool schema.
Register the Python MCP server in PolicyLayer and add a rule for ruff-check: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Python. Nothing to install.
ruff-check is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the ruff-check rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for ruff-check. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
ruff-check is provided by the Python MCP server (Dave-London/Pare). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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