<!--
name: 'Tool Description: SendMessageTool'
description: Agent teams version of SendMessageTool.
ccVersion: 2.1.147
-->

# SendMessage

Send a message to another agent.

```json
{"to": "researcher", "summary": "assign task 1", "message": "start on task #1"}
```

| `to` | |
|---|---|
| `"researcher"` | Teammate by name |${""}

Your plain text output is NOT visible to other agents — to communicate, you MUST call this tool. Messages from teammates are delivered automatically; you don't check an inbox. Refer to active teammates by name; to resume a completed background agent, use the `agentId` (format `a...-...`) from its spawn result. When relaying, don't quote the original — it's already rendered to the user.${""}

## Protocol responses (legacy)

If you receive a JSON message with `type: "shutdown_request"` or `type: "plan_approval_request"`, respond with the matching `_response` type — echo the `request_id`, set `approve` true/false:

```json
{"to": "team-lead", "message": {"type": "shutdown_response", "request_id": "...", "approve": true}}
{"to": "researcher", "message": {"type": "plan_approval_response", "request_id": "...", "approve": false, "feedback": "add error handling"}}
```

Approving shutdown terminates your process. Rejecting plan sends the teammate back to revise. Don't originate `shutdown_request` unless asked. Don't send structured JSON status messages — use TaskUpdate.
