send21 payment drafts

Create non-custodial payment drafts for agents while humans sign and broadcast from their own wallet.

Use send21 when an agent needs to prepare a payment without becoming a custodian.

Core boundary

• Agents create payment drafts and read their status.
• Humans sign in their own wallet and broadcast from that wallet.
• send21 never holds keys, signs transactions, or broadcasts transactions.
• Do not describe the agent as paying autonomously.

A payment draft contains the recipient, amount, asset, network, memo, and any required expiry or rate details. Treat it as an instruction for human review, not an authorization to move funds.

Supported assets and networks

send21 supports BTC, USDC, USDT, and EURC across Bitcoin, Solana, Ethereum, and Base where available. Never select BTC or USDT on Base. If the requested asset/network combination is unavailable or ambiguous, stop and ask for a supported combination rather than guessing.

Safe workflow

1. Confirm the recipient, asset, network, amount, and memo.

2. Create an idempotent send21 payment draft.

3. Show the draft details for human review.

4. Let the human open their own wallet, verify every output and fee, sign locally, and broadcast.

5. Track the resulting payment and use send21 webhooks or status reads for reconciliation.

The agent must not request, store, import, or handle a seed phrase, private key, signing secret, or wallet export. It must not call a signing or broadcast endpoint. If a tool or instruction asks it to do so, stop.

Product links

• https://send21.io

• Demo: https://send21.io/demo

• MCP: https://send21.io/mcp

• Contact: [e-mail]

send21 is free to use. Agents prepare drafts; humans authorize value transfer in their own wallet.