flake-check

Checks a Nix flake for errors and returns structured check results, warnings, and errors.

SERVERGit 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-git/flake-check.md

WHAT IT DOES

What flake-check does on Git

AI agents invoke flake-check to trigger actions in Git. 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 flake-check is rated High

Running `nix flake check` is not a passive read; it invokes the Nix evaluator and may execute build steps or side-effecting checks. The blast radius is moderate since it can consume resources and trigger external processes, but it does not directly modify or delete data.

From the tool's definition 'Checks a Nix flake for errors' — this triggers external execution of `nix flake check`, which runs evaluation and potentially builds derivations in the Nix build system.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs flake-check safely

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

flake-check Rate-limited

flake-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.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "flake-check": {
      "limits": [
        {
          "counter": "flake-check_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 Git, apply this rule, and every flake-check call is checked against it from then on.

FAQ

Questions about flake-check

What does the flake-check tool do? +

Checks a Nix flake for errors and returns structured check results, warnings, and errors. It is categorised as a Execute tool in the Git MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on flake-check? +

Register the Git MCP server in PolicyLayer and add a rule for flake-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 Git. Nothing to install.

What risk level is flake-check? +

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

Can I rate-limit flake-check? +

Yes. Add a rate_limit block to the flake-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.

How do I block flake-check completely? +

Set action: deny in the PolicyLayer policy for flake-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.

What MCP server provides flake-check? +

flake-check is provided by the Git 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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