mail_draft · Yaver MCP: Risk & Policy

WHAT IT DOES

What mail_draft does on Yaver

AI agents invoke mail_draft to trigger actions in Yaver. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

PARAMETERS

Parameter	Type	Required	Description
`id`	string	Yes
`runner`	string	—	Override default runner (claude / codex / opencode).
`execute`	boolean	—
`provider`	string	—
`instructions`	string	—

Parameters from the server's own tool schema.

WHY IT NEEDS A POLICY

Why mail_draft needs a policy

mail_draft triggers real processes with real consequences. An agent gone sideways doesn't fire it once — it starts dozens of builds, sends mass notifications, or burns through compute before anyone looks up.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

mail_draft Rate-limited

mail_draft stays usable, but rate-capped — a runaway agent can't fire it dozens of times 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_draft": {
      "limits": [
        {
          "counter": "mail_draft_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Yaver, so you can run agents against it safely.

FAQ

Questions about mail_draft

What does the mail_draft tool do? +

Draft a reply to a message. Pulls the thread + recent sent-folder mail for tone, then pipes through the configured AI runner when execute=true and returns the draft text. Otherwise returns the prompt the caller can execute manually. It is categorised as a Execute tool in the Yaver MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

What parameters does mail_draft accept? +

mail_draft accepts 5 parameters: id, runner, execute, provider, instructions. Required: id. The full parameter table on this page comes from the server's own tool schema.

How do I enforce a policy on mail_draft? +

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

What risk level is mail_draft? +

mail_draft is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit mail_draft? +

Yes. Add a rate_limit block to the mail_draft 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_draft completely? +

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

mail_draft is provided by the Yaver MCP server (yaver-cli). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.