Show HN: Send21 – Crypto pay links an AI agent can create but can't spend

Category: devtools

Tags: crypto-payments, ai-agents, mcp, payment-links, api

Score: 5.0/10 (Innovation: 6, Technical: 5, Documentation: 4, Utility: 4)

Send21 is a crypto payment-link service where AI agents can create payment drafts via API or MCP using scoped keys that cannot spend funds, requiring a human to sign the transaction in their own wallet. The draft-only scoping for agents is a sensible security model for agent-assisted payments, though the product is early and the demo README is minimal.

Target audience: backend devs and fintech integrators building agent-assisted payment flows

Repository: https://send21.io/demo

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