{"slug": "show-hn-send21-crypto-pay-links-an-ai-agent-can-create-but-can-t-spend", "title": "Show HN: Send21 – Crypto pay links an AI agent can create but can't spend", "summary": "Send21 launched a testnet demo of a crypto payment-link service in which an AI agent holds a scoped API key that can create and track payment drafts but cannot spend, since a human must sign each draft in their own wallet. The service, which never holds keys, signs or broadcasts, exposes the same draft-only flow over a REST API and an MCP server at send21.io/mcp, and notifies backends via a signed draft.confirmed webhook when a payment confirms on-chain. Send21 said account drafts run on live networks, and that a draft moves no money until someone signs it, so small live drafts to one's own address are a safe integration test.", "body_md": "**Testnet demo.** You sign with your own wallet, on test networks only. The coins are free test coins from public faucets and have no value.\n\n# Try send21 with a real test payment\n\nSee the whole flow in a few minutes, with no account and no email. send21 creates a payment draft, you pay it from your own wallet, and the page shows the confirmation from a public test network.\n\n## How it works\n\n1. send21 **creates a payment draft** , with the same draft-only access an AI agent gets. Nothing here can spend.\n2. You **check and sign in your own wallet** . send21 never holds keys, never signs and never broadcasts.\n3. send21 **watches the chain** until the payment confirms. In a real integration your backend gets a signed draft.confirmed webhook at that moment.\n\n## Need test coins? Faucets\n\n## For AI agents: the same flow over API or MCP\n\nAn agent gets a scoped API key that can **create and track drafts but never spend**. A person always signs in their own wallet. Test networks on send21.io are for this demo only, and account drafts use the live networks. That is still safe while you integrate: a draft moves no money until someone signs it, so create small drafts to your own address and cancel them.\n\n```\n# an AI agent (or your backend) creates the draft with a scoped key.\n# draft-only scopes: the key can create and track drafts but can never spend\n# a draft moves no money until a human signs it, so a small live draft is a safe test\ncurl -X POST https://send21.io/api/v1/drafts \\\n  -H \"Authorization: Bearer s21_YOUR_KEY\" \\\n  -H \"Content-Type: application/json\" \\\n  -H \"Idempotency-Key: agent-demo-001\" \\\n  -d '{\n    \"receiverAddress\": \"0x...your-own-address\",\n    \"network\": \"Base\",\n    \"currency\": \"Usdc\",\n    \"paymentMethod\": \"MultiOutput\",\n    \"singleOutput\": true,\n    \"amountSats\": 1000000,\n    \"memo\": \"agent integration test, 1 USDC\"\n  }'\n// MCP (Streamable HTTP), same key, same draft-only scopes\n{\n  \"mcpServers\": {\n    \"send21\": {\n      \"url\": \"https://send21.io/mcp\",\n      \"headers\": { \"Authorization\": \"Bearer s21_YOUR_KEY\" }\n    }\n  }\n}\n// then call the create_draft tool with { \"network\": \"Base\", \"currency\": \"Usdc\", ... }\n```\n\nFull API: [/swagger](https://send21.io/swagger/index.html) | agent overview: [/llms.txt](https://send21.io/llms.txt) | status via GET /drafts/{id}/status or signed webhooks (draft.confirmed).\n\n## Ready for real payments?\n\nCreate a free account and send your first pay link. No subscription, only a small fee per payment.", "url": "https://wpnews.pro/news/show-hn-send21-crypto-pay-links-an-ai-agent-can-create-but-can-t-spend", "canonical_source": "https://send21.io/demo", "published_at": "2026-10-30 08:26:44+00:00", "updated_at": "2026-10-30 08:46:58.827295+00:00", "lang": "en", "topics": ["ai-agents", "agent-protocols", "ai-tools"], "entities": ["Send21", "Base", "USDC", "MCP"], "also_reported_by": [], "alternates": {"html": "https://wpnews.pro/news/show-hn-send21-crypto-pay-links-an-ai-agent-can-create-but-can-t-spend", "markdown": "https://wpnews.pro/news/show-hn-send21-crypto-pay-links-an-ai-agent-can-create-but-can-t-spend.md", "text": "https://wpnews.pro/news/show-hn-send21-crypto-pay-links-an-ai-agent-can-create-but-can-t-spend.txt", "jsonld": "https://wpnews.pro/news/show-hn-send21-crypto-pay-links-an-ai-agent-can-create-but-can-t-spend.jsonld"}}