bash_command

Execute a bash command with detailed output and monitoring.

SERVERMCP Filesystem Server SOURCEa-niranjan/mcp-filesystem

High RISK CLASS

Category Execute

Parameters 00 required

Recommended Rate-limitedsee the rule below

Registry record Grade F, identity unverified Pull the record →

This record as markdown: /tools/a-niranjan-mcp-filesystem/bash-command.md

WHAT IT DOES

What bash_command does on MCP Filesystem Server

AI agents invoke bash_command to trigger actions in MCP Filesystem Server. 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.

RISK

Why bash_command is rated High

Bash command execution is a core Execute category risk because it can invoke arbitrary shell operations (loops, pipes, subshells, external tools) with outcomes dependent entirely on the command string argument. Even if constrained to 'predefined directories', bash grants access to environment variables, system utilities, and can perform reads, writes, deletions, or network operations depending on the command.

From the tool's definition Tool name 'bash_command' combined with description 'Execute a bash command' indicates arbitrary command execution.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs bash_command safely

PolicyLayer is an MCP gateway: it sits between your AI agents and MCP Filesystem Server, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For bash_command, this is the rule to start with:

bash_command Rate-limited

bash_command 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.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "bash_command": {
      "limits": [
        {
          "counter": "bash_command_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL → Instant setup, no code required.

The button opens the PolicyLayer dashboard: create your workspace, connect MCP Filesystem Server, apply this rule, and every bash_command call is checked against it from then on.

FAQ

Questions about bash_command

What does the bash_command tool do? +

Execute a bash command with detailed output and monitoring. It is categorised as a Execute tool in the MCP Filesystem Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on bash_command? +

Register the MCP Filesystem Server MCP server in PolicyLayer and add a rule for bash_command: 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 MCP Filesystem Server. Nothing to install.

What risk level is bash_command? +

bash_command is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit bash_command? +

Yes. Add a rate_limit block to the bash_command 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.

How do I block bash_command completely? +

Set action: deny in the PolicyLayer policy for bash_command. 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.

What MCP server provides bash_command? +

bash_command is provided by the MCP Filesystem Server MCP server (a-niranjan/mcp-filesystem). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

KEEP EXPLORING

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