Agent-ready email and SMS APIs
We scanned 11 transactional email, SMS and messaging APIs the way an AI agent would, and scored how well ChatGPT, Claude and Perplexity can read each one, sign a team up and connect through the API.
Which email or SMS API is best for AI agents?
It depends on what you need agents to do. If you want an agent to sign your team up and connect through the API, Bird scores highest (90/100), followed by Resend (89) and Postmark (83). Bird, Resend and Telnyx run remote MCP servers agents can connect to directly. Vonage blocks AI agents with a bot wall, so assistants can't read its site at all. Scores as of 3 Nov 2026.
| # | email or SMS API | Score /100 | Core /60 | Sign up /40 | API /40 | Bot wall | llms.txt | MCP | OpenAPI | Public pricing | Biggest gap |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | BirdRe-check live | 90 | 55 | 36 | 33 | · | ✓ | ✓ | · | ✓ | OpenAPI spec |
| 2 | ResendRe-check live | 89 | 51 | 36 | 40 | · | ✓ | ✓ | ✓ | ✓ | Semantic HTML (main, nav, header) |
| 3 | PostmarkRe-check live | 83 | 54 | 40 | 17 | · | ✓ | · | · | ✓ | Remote MCP server |
| 4 | PlivoRe-check live | 81 | 58 | 34 | 12 | · | ✓ | · | · | ✓ | Remote MCP server |
| 5 | SendGridRe-check live | 79 | 53 | 34 | 17 | · | ✓ | · | · | ✓ | Remote MCP server |
| 6 | TwilioRe-check live | 78 | 55 | 34 | 11 | · | ✓ | · | · | ✓ | Remote MCP server |
| 7 | SinchRe-check live | 78 | 53 | 30 | 20 | · | ✓ | · | · | ✓ | Remote MCP server |
| 8 | MailtrapRe-check live | 78 | 54 | 30 | 17 | · | ✓ | · | · | ✓ | Remote MCP server |
| 9 | MailgunRe-check live | 72 | 50 | 24 | 20 | · | ✓ | · | · | ✓ | Remote MCP server |
| 10 | TelnyxRe-check live | 67 | 44 | 6 | 40 | · | ✓ | ✓ | ✓ | · | Public pricing page |
| 11 | VonageRe-check live | 26 | 26 | 0 | 0 | blocks agents | ✓ | · | · | · | Agents get the real page, not a bot wall |
Automated, read-only scan of each homepage, robots.txt, llms.txt, docs, OpenAPI paths and MCP endpoints on 3 Nov 2026. Score = core + the average of Sign up and API, so the two job columns share 40 points. Scores can change; use "Re-check live" for today's result. How scoring works.
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Questions
Which email or SMS API is the most agent-ready?
Bird, with 90/100 in our scan on 3 Nov 2026.
Which email and SMS APIs block AI agents?
Vonage returned a bot challenge or a 403 to an AI user-agent.
How is the score calculated?
Out of 100: up to 60 core points for what every site needs (agents can reach and read it, structured data, llms.txt), plus the average of two job scores, each out of 40: letting an agent sign a team up (public pricing, an open sign-up page, a free plan) and letting it connect through the API (OpenAPI, MCP, self-serve keys, OAuth self-registration). For Bird: 55 + (36 + 33) ÷ 2, rounded, = 90.