Making an email API agent-native: llms.txt, a /api/me endpoint, and a zero-DNS sandbox sender

Short summary

Send16 transformed their email API from agent-compatible to agent-native by adding a zero-DNS sandbox sender, a /api/me bootstrap endpoint, and an llms.txt file documenting the raw HTTP contract. The key insight: for agents, onboarding IS the API — the first action must succeed without human intervention. They also built an MCP server with 79 tools and validated everything with a cold-agent test that completed end-to-end in four calls.

• •Agent-native APIs need a zero-friction first success — no DNS edits or out-of-band steps
• •llms.txt + /api/me bootstrap endpoint lets agents self-orient without SDKs or human help
• •MCP server ships 79 tools; cold-agent test passed end-to-end with no human intervention

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