# 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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