Send21

Send21 is a crypto payment tool that creates test network payment drafts and pay links for users and AI agents.

Send21 allows users and AI agents to make and test crypto payments across Bitcoin, Solana, Ethereum, Base, Arbitrum, and Polygon test networks. It creates payment drafts that allow individuals to sign transactions directly from their own wallets without the platform ever holding keys. AI agents can interact with the system via a full REST API or an MCP server using scoped keys that create drafts without spending capabilities. The platform includes features such as hosted pay pages, support for 161 currencies, signed webhooks, and recurring payments. Pricing relies on a per-payment fee ranging from 0.49% to 0.01% with no monthly subscription or setup costs.

Send21 at a glance

Best for: Software engineer
Runs on: Web, API
Pricing: No subscription; fees from 0.49% to 0.01% per payment, capped at $100
Released: October 2026
Category: AI agent tool
Website: send21.io

Key features

Create test network payment drafts
Support Bitcoin, Solana, Ethereum, Base, Arbitrum, and Polygon
REST API with scoped keys
MCP server for AI agents
Hosted pay pages with QR codes
Signed webhooks and email notifications
Recurring payments

Use it for

Test crypto pay links on public test networks
Enable AI agents to create payment drafts via API or MCP
Accept crypto payments across multiple blockchain networks
Process recurring payments daily, weekly, or monthly

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