shellcheck
Runs ShellCheck (shell script linter) and returns structured diagnostics (file, line, column, rule, severity, message).
This record as markdown: /tools/io-github-dave-london-github/shellcheck.md
What shellcheck does on Github
AI agents invoke shellcheck to trigger actions in Github. 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 shellcheck is rated High
The tool executes an external program (ShellCheck) against shell scripts. While it is read-only in intent (linting/static analysis), it actively runs an external process whose behavior depends on the input arguments. This falls under Execute. Misuse could involve pointing it at arbitrary files on the filesystem, but blast radius is limited since it only reads and reports diagnostics without modifying anything.
From the tool's definition Runs ShellCheck (shell script linter) and returns structured diagnostics
Attacks that exploit this kind of access
The rule that runs shellcheck safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Github, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For shellcheck, this is the rule to start with:
shellcheck 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 Github, apply this rule, and every shellcheck call is checked against it from then on.
Questions about shellcheck
Runs ShellCheck (shell script linter) and returns structured diagnostics (file, line, column, rule, severity, message). It is categorised as a Execute tool in the Github MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Github MCP server in PolicyLayer and add a rule for shellcheck: 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 Github. Nothing to install.
shellcheck 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 shellcheck 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 shellcheck. 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.
shellcheck is provided by the Github MCP server (@paretools/github). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
More on Github, and thousands of servers like it.
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