# Message headers for Agent Accounts

Source: https://developer.nylas.com/docs/changelogs/2026-08-17-agent-account-message-headers/

Agent Account grants now return message headers through the `fields` query parameter, the same way Google, Microsoft, and EAS grants do. Your agent can read the RFC threading chain straight off a message instead of tracking `thread_id` alone, which helps when a conversation crosses systems or you need to prove which message a reply answered.

## Added

- **`fields=include_headers` on Agent Accounts** returns the full header set on [Get Message](/docs/reference/api/messages/get-messages-id/), [Get all Messages](/docs/reference/api/messages/get-messages/), and [Send Message](/docs/reference/api/messages/send-message/). Agent Accounts join Google, Microsoft, and EAS as the providers that return the complete set. EWS and IMAP still return only the headers Nylas generates for MIME.

  ```bash
  curl --request GET \
    --url 'https://api.us.nylas.com/v3/grants/<NYLAS_GRANT_ID>/messages/<MESSAGE_ID>/?fields=include_headers' \
    --header 'Authorization: Bearer <NYLAS_API_KEY>'
  ```

- **`fields=include_basic_headers` on Agent Accounts** returns only the three RFC threading headers, `Message-ID`, `In-Reply-To`, and `References`. Use it when you're matching replies to sent messages and don't need the full header payload, which is often larger than the message body itself. With this addition, `include_basic_headers` works on all six providers: Google, Microsoft, EAS, EWS, IMAP, and Agent Accounts.

- Both options work on the [Send Message](/docs/reference/api/messages/send-message/) endpoint, so an agent gets the threading headers on the send response instead of making a follow-up `GET` call. This applies to synchronous sends; the parameter has no effect when you set `send_at`.

## Updated docs

- [Using email headers and MIME data](/docs/v3/email/headers-mime-data/) lists Agent Accounts in the provider support section for both options.
- [Supported endpoints for Agent Accounts](/docs/v3/agent-accounts/supported-endpoints/) documents both `fields` values on the Get Message row.
- [Email threading for agents](/docs/v3/agent-accounts/email-threading/) notes that both options also work on send.