mail_set_identity · Pyfastmail MCP: Risk & Policy

WHAT IT DOES

What mail_set_identity does on Pyfastmail

AI agents use mail_set_identity to create or update resources in Pyfastmail — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Pyfastmail environment.

WHY IT NEEDS A POLICY

Why mail_set_identity needs a policy

The tool name indicates a write operation that modifies account identity configuration. While the empty description limits certainty, the context of an email management system and the 'set_' prefix clearly indicate data modification rather than retrieval. This is categorized as Write rather than Execute because it modifies configuration data reversibly (identity settings can be changed again).

From the tool's definition Tool name 'mail_set_identity' combined with server description stating the MCP provides 'full access to Fastmail accounts for managing email' suggests this tool modifies email account identity settings.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

mail_set_identity Rate-limited

mail_set_identity 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": {
    "mail_set_identity": {
      "limits": [
        {
          "counter": "mail_set_identity_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 Pyfastmail, so you can run agents against it safely.

FAQ

Questions about mail_set_identity

What does the mail_set_identity tool do? +

mail_set_identity. It is categorised as a Write tool in the Pyfastmail MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on mail_set_identity? +

Register the Pyfastmail MCP server in PolicyLayer and add a rule for mail_set_identity: 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 Pyfastmail. Nothing to install.

What risk level is mail_set_identity? +

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

Can I rate-limit mail_set_identity? +

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

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

mail_set_identity is provided by the Pyfastmail MCP server (pjosols/pyfastmail-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.