contacts_update_contact · Pyfastmail MCP: Risk & Policy

WHAT IT DOES

What contacts_update_contact does on Pyfastmail

AI agents use contacts_update_contact 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 contacts_update_contact needs a policy

This tool updates contact information in a Fastmail account, which is a Write operation—it modifies data but does not irreversibly delete it. Severity is high because contact data often includes PII (personal identifiable information), and unauthorized modification could compromise user privacy or enable social engineering.

From the tool's definition Tool name 'contacts_update_contact' and sibling tool 'contacts_create_contact' and 'contacts_delete_contact' indicate a contacts management suite; 'update' modifies contact data reversibly.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

contacts_update_contact Rate-limited

contacts_update_contact 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": {
    "contacts_update_contact": {
      "limits": [
        {
          "counter": "contacts_update_contact_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 contacts_update_contact

What does the contacts_update_contact tool do? +

contacts_update_contact. 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 contacts_update_contact? +

Register the Pyfastmail MCP server in PolicyLayer and add a rule for contacts_update_contact: 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 contacts_update_contact? +

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

Can I rate-limit contacts_update_contact? +

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

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

contacts_update_contact 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.