flake-show
Shows the outputs of a Nix flake as a structured tree. Uses --json for machine-parseable output by default.
This record as markdown: /tools/io-github-dave-london-npm/flake-show.md
What flake-show does on Npm
AI agents call flake-show to retrieve information from Npm without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
Why flake-show is rated Low
This tool retrieves and displays information about Nix flake structure and outputs. It performs no modifications, deletions, or external operations—it simply queries and presents existing data in a structured format. This is characteristic of Read category tools.
From the tool's definition Tool 'flake-show' is described as showing outputs of a Nix flake in a structured tree format using --json. The verb 'shows' and the read-only nature of displaying flake outputs indicate this is a data retrieval operation with no side effects.
Attacks that exploit this kind of access
The rule that runs flake-show 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 flake-show, this is the rule to start with:
flake-show is read-only, so it stays allowed. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect Npm, apply this rule, and every flake-show call is checked against it from then on.
Questions about flake-show
Shows the outputs of a Nix flake as a structured tree. Uses --json for machine-parseable output by default. It is categorised as a Read tool in the Npm MCP Server, which means it retrieves data without modifying state.
Register the Npm MCP server in PolicyLayer and add a rule for flake-show: 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.
flake-show is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the flake-show 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 flake-show. 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.
flake-show 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.
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