prettier-format
Formats files with Prettier (--write) and returns a structured list of changed files.
This record as markdown: /tools/io-github-dave-london-github/prettier-format.md
What prettier-format does on Github
AI agents use prettier-format to create or update resources in Github, usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Github environment.
Why prettier-format is rated Medium
This tool modifies files reversibly by reformatting them. It does not execute arbitrary code, delete data, or cause financial harm. The write operation is reversible (files can be reformatted again or reverted), placing it squarely in the Write category. Severity is medium because an AI agent could maliciously reformat entire codebases, but damage is recoverable through version control.
From the tool's definition Tool description states it 'Formats files with Prettier (--write)' - the --write flag modifies files in place. Returns 'a structured list of changed files' confirming files are altered.
Attacks that exploit this kind of access
The rule that runs prettier-format 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 prettier-format, this is the rule to start with:
prettier-format stays usable, but capped: an agent stuck in a loop can't make hundreds of changes 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 prettier-format call is checked against it from then on.
Questions about prettier-format
Formats files with Prettier (--write) and returns a structured list of changed files. It is categorised as a Write tool in the Github MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Github MCP server in PolicyLayer and add a rule for prettier-format: 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.
prettier-format is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the prettier-format 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 prettier-format. 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.
prettier-format 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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