Write content to a file. Args: file_path: Path to the file to write content: Content to write overwrite: Whether to overwrite if exists
AI agents use write_file to create or update resources in MCP Python Interpreter — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your MCP Python Interpreter environment.
This tool creates or modifies files reversibly. While not destructive by itself (overwrite is optional and content can be recovered), it poses medium severity risk in an AI agent context: malicious file writes could corrupt application configurations, inject malicious code into source files, or modify security-critical settings.
From the tool's definition Tool name 'write_file' and description 'Write content to a file' with 'overwrite' parameter indicate file creation and modification capability.
Documented attack patterns abuse exactly the kind of access write_file gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and MCP Python Interpreter, and nothing reaches the server without passing your rules. This is the rule we recommend for write_file:
{
"version": "1",
"default": "deny",
"tools": {
"write_file": {
"limits": [
{
"counter": "write_file_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}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.
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Write content to a file. Args: file_path: Path to the file to write content: Content to write overwrite: Whether to overwrite if exists. It is categorised as a Write tool in the MCP Python Interpreter MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the MCP Python Interpreter 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 MCP Python Interpreter. Nothing to install.
write_file 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 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.
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.
write_file is provided by the MCP Python Interpreter MCP server (yzfly/mcp-python-interpreter). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 10 MCP Python Interpreter tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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10 MCP Python Interpreter tools catalogued and risk-classified — across an index of 42,500+ MCP servers.