register_agent · MCP Agent Mail MCP: Risk & Policy

WHAT IT DOES

What register_agent does on MCP Agent Mail

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

WHY IT NEEDS A POLICY

Why register_agent needs a policy

Registration typically creates new agent records or modifies identity state, which qualifies as Write (reversible data modification). Severity is medium due to potential for agent spoofing or unauthorized agent registration affecting multi-agent coordination, though effects are reversible. Confidence reduced to 0.75 because the tool description is empty, requiring inference from context and naming.

From the tool's definition Tool name 'register_agent' combined with server context describing 'identities' and 'coordination layer for coding agents' indicates agent registration/identity creation.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

register_agent Rate-limited

register_agent 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_agent": {
      "limits": [
        {
          "counter": "register_agent_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 MCP Agent Mail, so you can run agents against it safely.

FAQ

Questions about register_agent

What does the register_agent tool do? +

register_agent. It is categorised as a Write tool in the MCP Agent Mail 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_agent? +

Register the MCP Agent Mail MCP server in PolicyLayer and add a rule for register_agent: 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 Agent Mail. Nothing to install.

What risk level is register_agent? +

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

Can I rate-limit register_agent? +

Yes. Add a rate_limit block to the register_agent 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_agent completely? +

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

register_agent is provided by the MCP Agent Mail MCP server (omelchmichael/mcp_agent_mail). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.