flake-update

Updates flake lock file inputs and returns structured information about what was updated.

SERVERBuild SOURCEDave-London/Pare

Medium RISK CLASS

Category Write

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-build/flake-update.md

WHAT IT DOES

What flake-update does on Build

AI agents use flake-update to create or update resources in Build, usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Build environment.

RISK

Why flake-update is rated Medium

The tool performs a Write operation because it modifies a configuration/lockfile artifact (flake.lock). While it changes version pins and dependency specifications, this is reversible through standard version control practices and does not permanently destroy data.

From the tool's definition 'Updates flake lock file inputs' - this modifies the flake.lock file, which is a lockfile that tracks dependency versions and integrity hashes in Nix environments.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs flake-update safely

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

flake-update Rate-limited

flake-update 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.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "flake-update": {
      "limits": [
        {
          "counter": "flake-update_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL → Instant setup, no code required.

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

FAQ

Questions about flake-update

What does the flake-update tool do? +

Updates flake lock file inputs and returns structured information about what was updated. It is categorised as a Write tool in the Build MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

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

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

What risk level is flake-update? +

flake-update is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit flake-update? +

Yes. Add a rate_limit block to the flake-update 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-update completely? +

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

flake-update is provided by the Build 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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Guides

Govern customer-ops agents →Argument validation →Scoped token →