Developer docs
Everything you need to create payment requests and drafts from your own code or from an AI agent. send21 prepares payment instructions; the payer always signs in their own wallet, and send21 never holds keys or funds.
Start here
- API quickstart: API keys, your first payment request and draft, status and idempotency.
- Webhooks: events, payloads, retries and signature checks.
- MCP server: connect an AI agent over the Model Context Protocol.
- Currencies and networks: which assets each network carries, decimals and confirmations.
- Lightning: pay links and drafts that confirm through the receiver's Lightning address.
Machine-readable references
- OpenAPI 3 specification: /openapi.json, browsable at /swagger.
- Overview for language models: /llms.txt, with every doc in one file at /llms-full.txt.
- Every docs page is also available as Markdown: add
.mdto the address, for example /docs/webhooks.md.
Try it without an account
The testnet demo runs the whole flow on test networks with free test coins: a draft, a QR payment from your own wallet, and an on-chain confirmation. No account and no email.
Related
This page is also available as Markdown: /docs.md. Questions: [email protected].