biome-check
Runs Biome check (lint + format) and returns structured diagnostics (file, line, rule, severity, message).
This record as markdown: /tools/io-github-dave-london-github/biome-check.md
What biome-check does on Github
AI agents invoke biome-check to trigger actions in Github. 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.
Why biome-check is rated High
This tool runs an external process (Biome linter/formatter) on code, which constitutes execution of an external operation. While it appears read-only in intent (returning diagnostics), it actively executes a CLI tool whose side effects depend on arguments. Severity is medium because a misconfigured or malicious invocation could affect files or consume significant resources, though the primary use case is diagnostic.
From the tool's definition 'Runs Biome check (lint + format)' — the tool actively executes the Biome CLI tool against code
Attacks that exploit this kind of access
The rule that runs biome-check safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Github, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For biome-check, this is the rule to start with:
biome-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 Github, apply this rule, and every biome-check call is checked against it from then on.
Questions about biome-check
Runs Biome check (lint + format) and returns structured diagnostics (file, line, rule, severity, message). It is categorised as a Execute tool in the Github MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Github MCP server in PolicyLayer and add a rule for biome-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 Github. Nothing to install.
biome-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 biome-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 biome-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.
biome-check is provided by the Github MCP server (@paretools/github). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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