Formats files with Biome (format --write) and returns a structured list of changed files.
AI agents use biome-format to create or update resources in Make — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Make environment.
The tool writes changes to files by formatting them with Biome. While formatting is generally reversible (the original unformatted code is not deleted, just modified), this is a Write operation that alters file contents. Severity is medium because the effect is reversible and limited to code formatting without data loss, but an agent could inadvertently format files in unintended ways or formats.
From the tool's definition Tool description states 'Formats files with Biome (format --write) and returns a structured list of changed files.' The --write flag modifies files in place.
Documented attack patterns abuse exactly the kind of access biome-format gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Make, and nothing reaches the server without passing your rules. This is the rule we recommend for biome-format:
{
"version": "1",
"default": "deny",
"tools": {
"biome-format": {
"limits": [
{
"counter": "biome-format_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}biome-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.
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Formats files with Biome (format --write) and returns a structured list of changed files. It is categorised as a Write tool in the Make MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Make MCP server in PolicyLayer and add a rule for biome-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 Make. Nothing to install.
biome-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 biome-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 biome-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.
biome-format is provided by the Make MCP server (Dave-London/Pare). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Make, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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