register_sender_domain · Run402 MCP: Risk & Policy

WHAT IT DOES

What register_sender_domain does on Run402

AI agents use register_sender_domain to create or update resources in Run402 — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Run402 environment.

WHY IT NEEDS A POLICY

Why register_sender_domain needs a policy

This is a reversible configuration change (Write category) rather than Read, Execute, or Destructive. It creates/registers a new email domain setting for the project. Severity is medium because misconfiguration could enable email spoofing or abuse of the project's domain, and an AI agent could register unauthorized domains on behalf of a victim project.

From the tool's definition Tool registers/configures a custom email sending domain, returning DNS records to be added. The description indicates this modifies email sending configuration for a project ('email sends from your domain instead of mail.run402.com').

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

register_sender_domain Rate-limited

register_sender_domain 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": {
    "register_sender_domain": {
      "limits": [
        {
          "counter": "register_sender_domain_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 Run402, so you can run agents against it safely.

FAQ

Questions about register_sender_domain

What does the register_sender_domain tool do? +

Register a custom email sending domain for a project. Returns DNS records (DKIM CNAMEs + SPF/DMARC) to add. Once verified, email sends from your domain instead of mail.run402.com. It is categorised as a Write tool in the Run402 MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on register_sender_domain? +

Register the Run402 MCP server in PolicyLayer and add a rule for register_sender_domain: 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 Run402. Nothing to install.

What risk level is register_sender_domain? +

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

Can I rate-limit register_sender_domain? +

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

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

register_sender_domain is provided by the Run402 MCP server (kychee-com/run402). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.