fmt
Checks or fixes Rust formatting and returns structured output.
This record as markdown: /tools/io-github-dave-london-docker/fmt.md
What fmt does on Docker
AI agents invoke fmt to trigger actions in Docker. 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 fmt is rated High
The tool runs a formatting operation (likely `rustfmt`) on Rust code. When in 'fix' mode it modifies files in place, and it executes an external process. The most severe applicable category is Execute since it runs an external tool and may modify files. Confidence is moderate because the description is brief and context (Docker server with misc tools) is unusual for a Rust formatter.
From the tool's definition Checks or fixes Rust formatting and returns structured output
Attacks that exploit this kind of access
The rule that runs fmt safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Docker, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For fmt, this is the rule to start with:
fmt 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 Docker, apply this rule, and every fmt call is checked against it from then on.
Questions about fmt
Checks or fixes Rust formatting and returns structured output. It is categorised as a Execute tool in the Docker MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Docker MCP server in PolicyLayer and add a rule for fmt: 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 Docker. Nothing to install.
fmt 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 fmt 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 fmt. 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.
fmt is provided by the Docker MCP server (@paretools/docker). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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