<Info>This API is in beta. Endpoints, fields, and behavior may still change, so avoid depending on it in production.</Info>

Adds a reply to a comment thread. Replying to a resolved thread doesn't reopen it.

mentioned_emails records who the comment mentions. Only emails that List mentionable users returns are kept, and the rest are dropped without an error. Mentioning someone sends them no email or notification, and responses never return the list.

Anyone with the app open in the builder sees the change right away.

This is limited to 120 requests per minute per app, shared by every other comments endpoint. A signed-in session has its own limit, and every personal access token for the workspace shares one. Some workspaces have a different limit. Every request that counts against the limit gets X-RateLimit-Limit, X-RateLimit-Remaining and X-RateLimit-Reset (Unix time in seconds) headers, and a 429 also gets Retry-After in seconds. If the limiter itself is unavailable, requests go through without these headers.

<Note>Call this as an editor of the app, with a personal access token sent as a Bearer token or from a signed-in session. Viewers in the app's workspace, read-only tokens, and workspace API keys are refused.</Note>

{
  "content": "Done, thanks!",
  "mentioned_emails": [
    "dana@acme.com"
  ]
}

{
  "id": "68e2b7c4d4f0a9001c3e5a1c",
  "content": "Make this button match the header color.",
  "sender_id": "6820f41be7b91d003c45a20a",
  "sender_name": "Dana Levi",
  "sender_avatar_url": "https://lh3.googleusercontent.com/a/ACg8ocJ2",
  "created_date": "2026-10-05T09:14:22.512000Z",
  "edited_at": "2026-10-05T09:14:22.512000Z",
  "reactions": {
    "👍": [
      "6820f41be7b91d003c45a20a"
    ]
  }
}