AI agents use file_modify to create or update resources in MCP Terminal — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your MCP Terminal environment.
This tool creates or modifies file data reversibly. While it modifies files, it does not irreversibly delete or destroy data (which would be Destructive), nor does it execute code or commands (which would be Execute).
From the tool's definition Tool name 'file_modify' and description 'Writes content to a file' explicitly describe modification of file content.
Documented attack patterns abuse exactly the kind of access file_modify gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and MCP Terminal, and nothing reaches the server without passing your rules. This is the rule we recommend for file_modify:
{
"version": "1",
"default": "deny",
"tools": {
"file_modify": {
"limits": [
{
"counter": "file_modify_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}file_modify 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.
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Writes content to a file. It is categorised as a Write tool in the MCP Terminal MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the MCP Terminal MCP server in PolicyLayer and add a rule for file_modify: 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 Terminal. Nothing to install.
file_modify is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the file_modify 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 file_modify. 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.
file_modify is provided by the MCP Terminal MCP server (sichang824/mcp-terminal). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from MCP Terminal, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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3 MCP Terminal tools catalogued and risk-classified — across an index of 43,000+ MCP servers.