write_file · Agent-VC MCP Server MCP: Risk & Policy

WHAT IT DOES

What write_file does on Agent-VC MCP Server

AI agents use write_file to create or update resources in Agent-VC MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Agent-VC MCP Server environment.

WHY IT NEEDS A POLICY

Why write_file needs a policy

This tool creates or modifies file content in what is described as a 'sandboxed environment' with version control (Fossil SCM). The write operation is reversible via the version control system (evidenced by sibling tools like 'vc_commit' and 'vc_diff').

From the tool's definition Tool name is 'write_file' and description states 'Write content to a file in a project'. The verb 'write' and the action of modifying file content directly indicate a Write operation that creates or modifies data reversibly.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

write_file Rate-limited

write_file stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "write_file": {
      "limits": [
        {
          "counter": "write_file_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Agent-VC MCP Server, so you can run agents against it safely.

FAQ

Questions about write_file

What does the write_file tool do? +

Write content to a file in a project. It is categorised as a Write tool in the Agent-VC MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on write_file? +

Register the Agent-VC MCP Server MCP server in PolicyLayer and add a rule for write_file: 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 Agent-VC MCP Server. Nothing to install.

What risk level is write_file? +

write_file is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit write_file? +

Yes. Add a rate_limit block to the write_file 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 write_file completely? +

Set action: deny in the PolicyLayer policy for write_file. 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 write_file? +

write_file is provided by the Agent-VC MCP Server MCP server (manbothq/agent-vc-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.