@three-ws/herald-mcp

Let your agent tell you something in person.

An MCP server with one idea behind it: when an agent finishes something that mattered, or gets stuck, it should not add a line to a log you will never scroll back to. It should walk up to you and say so.

Wire this in, and it does. Your own 3D companion appears in the corner of whatever browser tab you have open, gestures, and says the line out loud, with a link to click through.

you: run the migration, then the backfill, and tell me when it's done
agent: [runs for 22 minutes]
       [calls announce_result: task "the backfill", outcome succeeded, 1320s]
your browser: your avatar walks on: "the backfill finished in 22m"

Tools

Install

npx -y @three-ws/herald-mcp

Claude Code:

claude mcp add herald -e THREE_WS_API_KEY=sk_live_... -- npx -y @three-ws/herald-mcp

Claude Desktop / Cursor (mcp.json):

{
  "mcpServers": {
    "herald": {
      "command": "npx",
      "args": ["-y", "@three-ws/herald-mcp"],
      "env": { "THREE_WS_API_KEY": "sk_live_..." }
    }
  }
}

The key

Create one at three.ws/dashboard/developers with the herald:announce scope, and put it in THREE_WS_API_KEY.

An announcement is always delivered to the key owner's own live sessions. There is no recipient parameter: this server cannot be pointed at anybody else, so the worst a leaked key can do is annoy the person who leaked it. Revoke it in the same place.

When to use it (and when not to)

Announcements are scarce on purpose. The receiving client applies an importance floor, a rate limit, dedupe, quiet hours, and a freshness window, so anything that does not clear the bar is dropped rather than queued. That is the feature: an interruption only works while it is rare.

Good: a long job finished, a job failed, a decision is needed, something broke, money moved.

Bad: progress updates, "starting step 3 of 7", anything the person can read later. Those belong in the notification inbox (@three-ws/notifications-mcp).

If nothing is open to hear it, the line expires in about five minutes. The rail is a live channel, not an archive.

Example calls

// something broke, and it should wake somebody up
{ "name": "announce", "arguments": {
    "text": "The payments worker has been failing for 10 minutes",
    "from": "watchdog", "importance": 95, "tone": "error",
    "url": "https://three.ws/dashboard", "key": "payments-worker-down" } }

// a long task finished, and it should not
{ "name": "announce_result", "arguments": {
    "task": "the nightly backfill", "outcome": "succeeded", "seconds": 1320 } }

// wiring check
{ "name": "check_rail", "arguments": { "note": "claude-code" } }

How it reaches a browser

POST /api/herald/announce queues the line on the account's rail; the page listens over SSE and hands it to @three-ws/herald, which decides whether it clears the person's own rules and then delivers it through the 3D companion (or an accessible card when there is no GPU).

Try the whole loop, including the rules engine, at three.ws/herald.

License

Apache-2.0.