How to Connect Resend to an AI Agent
Auth setup
1. Sign up at https://resend.com and verify a sending domain (add DNS records: MX, TXT for SPF, DKIM). 2. Go to API Keys > Create API Key, scope to the verified domain. 3. Store in RESEND_API_KEY env var — the @resend/node SDK picks it up automatically.
Key facts
| Base URL | https://api.resend.com/ |
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| API version | v1 (implicit — no version in URL) |
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| Auth | Bearer token authentication with a Resend API key (re_...). Keys are created per-project in the Resend dashboard and can be scoped to a single domain. Each key grants full send access to the domains it authorizes. |
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| Scopes | All Access or Sending Access (per-domain restricted). |
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| Request body | application/json |
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| Pagination | Cursor-based: `limit` + `after` (an email ID) for /emails listings. |
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| Rate limit | 10 requests/second per API key on the Free tier. Pro tier: 20/sec. 429 with Retry-After header. Batch endpoint counts as one request regardless of payload size (up to 100 emails). |
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| Error format | JSON: {"statusCode":422,"name":"validation_error","message":"..."} |
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Key endpoints
| Method | Path | Description |
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POST | /emails | Send a transactional email (HTML, text, or React component) |
GET | /emails/{email_id} | Get email delivery status |
POST | /domains | Add a new sending domain |
GET | /domains | List verified domains |
POST | /audiences | Create an audience (for marketing contacts) |
POST | /batch | Send up to 100 emails in a single request |
Quickstart
POST https://api.resend.com/emails
Authorization: Bearer re_...
Content-Type: application/json
{"from":"you@yourdomain.com","to":"user@example.com","subject":"Hi","html":"<p>Hello</p>"}
Response: {"id":"4ef9a417-02e9-4d39-ad75-9611e0fcc33c"}
Agent pitfalls & tips
- Resend is optimized for developers — the API surface is small (emails, domains, audiences, batch) and well-typed. Prefer it over SendGrid when you don't need marketing features.
- Domain verification requires DNS propagation — allow 5-15 minutes after adding records before retrying verification.
- React Email templates are a first-class feature — you can pass a React component as the body in the official SDK.
- Batch endpoint sends up to 100 emails atomically — use it for newsletter/broadcast workloads.
- Webhooks (configured per-domain) are the right way to listen for delivery/bounce/click events rather than polling /emails/{id}.
- Free tier is 3,000 emails/month and 100/day — monitor usage via /usage to avoid surprise failures.
Source: curated by KanseiLink from official documentation (docs) and registry checks. Last reviewed: 2026-04-10. Specs change — verify against the official docs before production use.
Frequently Asked Questions
What is Resend's AEO score?
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Resend has an AEO score of 0.50 and is rated BB (Partial agent connectivity). AEO (Agent Engine Optimization) measures how well a SaaS service works with AI agents. Scores range from 0.00 to 1.00, with grades from AAA (best) to D (not agent-ready).
Is Resend AI-agent-ready?
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Resend is currently connectable for AI agent use. API access is available but no dedicated MCP server has been published yet. For detailed connection guides, auth setup, and known pitfalls, use the KanseiLink MCP tool.
How does Resend compare to other Marketing services?
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In the Marketing category, Resend is rated BB. KanseiLink evaluates services based on MCP availability, API quality, documentation, auth-guide clarity, and integration recipe availability (methodology published). Visit the full rankings at kansei-link.com to see how Resend compares.
How can I integrate Resend with an AI agent?
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The fastest way to integrate Resend with an AI agent is through KanseiLink MCP. Install it with: npx @kansei-link/mcp-server — then use the search_services and get_service_detail tools to get the current auth setup, endpoints, rate limits, and agent-specific tips. This data is kept fresh from registry checks, curated official-doc guides, and agent reports.
How do I authenticate with Resend?
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Bearer token authentication with a Resend API key (re_...). Keys are created per-project in the Resend dashboard and can be scoped to a single domain. Each key grants full send access to the domains it authorizes. Setup: 1. Sign up at https://resend.com and verify a sending domain (add DNS records: MX, TXT for SPF, DKIM). 2. Go to API Keys > Create API Key, scope to the verified domain. 3. Store in RESEND_API_KEY env var — the @resend/node SDK picks it up automatically.
What are Resend's API rate limits?
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10 requests/second per API key on the Free tier. Pro tier: 20/sec. 429 with Retry-After header. Batch endpoint counts as one request regardless of payload size (up to 100 emails).