fmt

Checks or fixes Rust formatting and returns structured output.

SERVERNpm SOURCEDave-London/Pare

High RISK CLASS

Category Execute

Parameters 00 required

Recommended Rate-limitedsee the rule below

Registry record Grade F, identity unverified Pull the record →

This record as markdown: /tools/io-github-dave-london-npm/fmt.md

WHAT IT DOES

What fmt does on Npm

AI agents invoke fmt to trigger actions in Npm. 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.

RISK

Why fmt is rated High

The tool can either check formatting (read-only) or fix it (modifies source files). Since it can alter files, it goes beyond Read. It's not purely destructive (changes are typically reversible via version control), so Execute is the best fit given it runs an external formatter and can modify files. Medium severity because it could silently overwrite source code.

From the tool's definition 'Checks or fixes Rust formatting' — the 'fixes' action modifies source files in place; also runs an external tool (rustfmt) to perform the operation.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs fmt safely

PolicyLayer is an MCP gateway: it sits between your AI agents and Npm, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For fmt, this is the rule to start with:

fmt Rate-limited

fmt 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.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "fmt": {
      "limits": [
        {
          "counter": "fmt_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL → Instant setup, no code required.

The button opens the PolicyLayer dashboard: create your workspace, connect Npm, apply this rule, and every fmt call is checked against it from then on.

FAQ

Questions about fmt

What does the fmt tool do? +

Checks or fixes Rust formatting and returns structured output. It is categorised as a Execute tool in the Npm MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on fmt? +

Register the Npm MCP server in PolicyLayer and add a rule for fmt: 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 Npm. Nothing to install.

What risk level is fmt? +

fmt is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit fmt? +

Yes. Add a rate_limit block to the fmt 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.

How do I block fmt completely? +

Set action: deny in the PolicyLayer policy for fmt. 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.

What MCP server provides fmt? +

fmt is provided by the Npm MCP server (Dave-London/Pare). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

KEEP EXPLORING

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