Executes a shell command for each item in a previously created list. Commands run in batches of ${BATCH_SIZE} parallel processes, with stdout and stderr streamed to separate files. WHEN TO USE: - Running the same shell command across multiple files (e.g., linting, formatting, compiling) - Batch p...
AI agents invoke run_shell_across_list to trigger actions in Par5. 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.
This tool allows execution of arbitrary shell commands whose effects are entirely dependent on the arguments provided. While shell commands can theoretically include destructive operations (rm, dd, etc.), the primary category is Execute because the tool itself is a generic command runner, not specifically designed for deletion.
From the tool's definition Tool description states it 'Executes a shell command for each item in a previously created list' and 'Commands run in batches of ${BATCH_SIZE} parallel processes'.
Documented attack patterns abuse exactly the kind of access run_shell_across_list gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Par5, and nothing reaches the server without passing your rules. This is the rule we recommend for run_shell_across_list:
{
"version": "1",
"default": "deny",
"tools": {
"run_shell_across_list": {
"limits": [
{
"counter": "run_shell_across_list_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}run_shell_across_list 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.
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Executes a shell command for each item in a previously created list. Commands run in batches of ${BATCH_SIZE} parallel processes, with stdout and stderr streamed to separate files. WHEN TO USE: - Running the same shell command across multiple files (e.g., linting, formatting, compiling) - Batch processing with command-line tools - Any operation where you need to execute shell commands on a collection of items HOW IT WORKS: 1. Each item in the list is substituted into the command where $item appears 2. Commands run in batches of ${BATCH_SIZE} at a time to avoid overwhelming the system 3. Output streams directly to files as the commands execute 4. This tool waits for all commands to complete before returning AFTER COMPLETION: - Read the stdout files to check results - Check stderr files if you encounter errors or unexpected output - Files are named based on the item (e.g.,. It is categorised as a Execute tool in the Par5 MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Par5 MCP server in PolicyLayer and add a rule for run_shell_across_list: 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 Par5. Nothing to install.
run_shell_across_list 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 run_shell_across_list 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 run_shell_across_list. 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.
run_shell_across_list is provided by the Par5 MCP server (mathematic-inc/par5-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Par5, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
8 Par5 tools catalogued and risk-classified — across an index of 43,000+ MCP servers.