develop
Enters or queries a Nix dev shell. When a command is provided, runs it inside the dev shell and returns the result.
This record as markdown: /tools/io-github-dave-london-cargo/develop.md
What develop does on Cargo
AI agents invoke develop to trigger actions in Cargo. 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.
Why develop is rated High
When a command is provided, this tool executes it inside a dev shell, meaning arbitrary code execution is possible. The blast radius is high because commands run in a shell environment can have wide-ranging effects on the system, files, and processes.
From the tool's definition 'runs it inside the dev shell and returns the result' — executes arbitrary commands within a Nix dev shell environment
Attacks that exploit this kind of access
The rule that runs develop safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Cargo, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For develop, this is the rule to start with:
develop 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.
The button opens the PolicyLayer dashboard: create your workspace, connect Cargo, apply this rule, and every develop call is checked against it from then on.
Questions about develop
Enters or queries a Nix dev shell. When a command is provided, runs it inside the dev shell and returns the result. It is categorised as a Execute tool in the Cargo MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Cargo MCP server in PolicyLayer and add a rule for develop: 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 Cargo. Nothing to install.
develop is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the develop 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 develop. 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.
develop is provided by the Cargo 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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