build
Runs a build command and returns structured success/failure with errors and warnings.
This record as markdown: /tools/io-github-dave-london-cargo/build.md
What build does on Cargo
AI agents invoke build 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 build is rated High
The tool executes an external build command (cargo build), which can trigger arbitrary code execution during the compilation process (build scripts, procedural macros, dependencies). While the primary intent is compilation rather than arbitrary command execution, it still constitutes Execute category as it runs code whose effects depend on the project contents and build configuration.
From the tool's definition Tool description states it 'Runs a build command' which executes code compilation. The server description emphasizes 'Structured Rust cargo operations (build, test, clippy)' indicating these are code execution operations.
Attacks that exploit this kind of access
The rule that runs build 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 build, this is the rule to start with:
build 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 build call is checked against it from then on.
Questions about build
Runs a build command and returns structured success/failure with errors and warnings. 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 build: 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.
build 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 build 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 build. 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.
build 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.
More on Cargo, and thousands of servers like it.
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