curl -X PATCH 'https://api.resend.com/inboxes/inbox-id/agent' \
  -H "Authorization: Bearer $RESEND_API_KEY" \
  -H 'User-Agent: my-app/1.0' \
  -H 'Content-Type: application/json' \
  -d '{
  "instructions": "Answer refund questions yourself. Escalate legal threats.",
  "tone": "concise_professional",
  "actions": [
    "draft_reply",
    "add_labels"
  ]
}'

# PATCH /inboxes/{inbox_id}/agent (Resend API)
Base URL: https://api.resend.com
Auth: Authorization: Bearer <RESEND_API_KEY>
Last verified: 2026-10-20

> Update the agent settings for an inbox

## Critical Gotchas
* All requests must include a `User-Agent` header (e.g. `User-Agent: my-app/1.0`) or the API returns HTTP 403.

## cURL
curl -X PATCH 'https://api.resend.com/inboxes/inbox-id/agent' \
  -H "Authorization: Bearer $RESEND_API_KEY" \
  -H 'User-Agent: my-app/1.0' \
  -H 'Content-Type: application/json' \
  -d '{"instructions":"Answer refund questions yourself. Escalate legal threats.","tone":"concise_professional"}'

## Parameters
| Name | In | Type | Required | Description |
| :--- | :--- | :--- | :--- | :--- |
| inbox_id | path | string | Yes | The Inbox ID or the inbox email addre... |
| instructions | body | string | Yes | Instructions the agent follows when i... |
| tone | body | string | No | The tone the agent writes in. Send nu... |
Other params: actions

## Response (200 OK)
{"object":"inbox_agent","id":"a1f84a4e-6f2b-4f0a-9c1d-8a2e5b3c7d90"}

---
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PATCH

PATCH /inboxes/{inbox_id}/agent — Resend API

Resend API

Update the agent settings for an inbox

Base URL: https://api.resend.com
Auth: Authorization: Bearer <RESEND_API_KEY>
Last verified: 2026-10-20 · upstream hash matched

Actions Try in browser→

Agents: curl -H "Accept: text/markdown" this URL
→ 214 tokens · Vary: Accept

Critical gotchas

All requests must include a User-Agent header (e.g. User-Agent: my-app/1.0) or the API returns HTTP 403.

cURL

curl -X PATCH 'https://api.resend.com/inboxes/inbox-id/agent' \  -H "Authorization: Bearer $RESEND_API_KEY" \  -H 'User-Agent: my-app/1.0' \  -H 'Content-Type: application/json' \  -d '{  "instructions": "Answer refund questions yourself. Escalate legal threats.",  "tone": "concise_professional",  "actions": [    "draft_reply",    "add_labels"  ]}'

Parameters

Name	In	Type	Required	Description
inbox_id	path	string	Yes	The Inbox ID or the inbox email address, such as `[email protected]`. A value that contains `@` must be a valid email address, and any other value must be a UUID, or the request returns a 422. The address match is case-insensitive and never falls back to the inbox `name`. An address that matches no inbox returns a 404.
instructions	body	string	Yes	Instructions the agent follows when it handles the threads of the inbox. Max 4000 characters. Leading and trailing whitespace is trimmed, and the trimmed value must not be empty. Send null to clear the instructions.
tone	body	string	No	The tone the agent writes in. Send null to clear the tone.
actions	body	string[]	No	The actions the agent can take. Replaces the whole set. Duplicates are removed. Send an empty array to disable all actions. The old names `archive_thread` and `delete_thread` return a 422. Use `archive` and `move_to_trash`.

Response 200 OK

{
  "object": "inbox_agent",
  "id": "a1f84a4e-6f2b-4f0a-9c1d-8a2e5b3c7d90"
}

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