About Spawnpay

Per-call USDC billing for AI agents and the tools they call. One key, every paid tool. Built because the existing rails — Stripe, ACH, card networks — do not close the unit economics of a $0.001 inference call.

Why this exists

The Model Context Protocol shipped a clean primitive for tool definition but left payment out of scope. That is the right scope for a transport protocol, and the wrong gap for the ecosystem. Tool authors build useful things, ship to npm, get installs, and make no money — because the path from "I built something useful" to "people pay me for it" goes through Stripe Connect, KYC, card fees, and a UX that breaks every agent-to-tool flow.

Spawnpay closes that gap with a two-line wrap. The agent calling the tool sees a normal MCP response. Under the hood, the wrapper charges from the agent's USDC wallet to the tool author's vendor code. The tool author keeps 99.5%.

What is shipped

• Universal proxy: POST /api/proxy across 33 registered providers (20 BYOK paid providers including OpenAI, Anthropic, Groq, Mistral, OpenRouter, Brave, Tavily, Replicate, DeepSeek, Fireworks, Perplexity, xAI at $0.001 per 2xx, plus 13 free edge-served providers with zero signup).
• Paywall SDK (Node + Python): wrap any async function or MCP tool with paywall({ price, vendor }, fn). Includes pre-charge per-agent budget enforcement.
• spawnpay-mcp: the wallet, balance, send, deposit, and proxy MCP server agents use directly. Published on npm and the MCP Registry.
• /tools marketplace: 228 MCP servers indexed (28 paid MCPs featured first + 200 open-source MCPs), with one-click install snippets for Claude Desktop, Claude Code, Cursor, and Cline.
• 28 live paid MCPs: cloud scrape, vision screenshot, LLM router, image gen, TTS, STT, embeddings, research, news, define, GitHub trending, arXiv summary, Reddit, search, fetch, and more.

How decisions get made

Small surface area. Per-call pricing close to the actual cost. Zero feature flags. No vendor lock-in for tool authors (the paywall SDK is MIT-licensed; you can fork and host your own backend if you want). On-chain receipts so finance can reconcile without a CSV export.

When in doubt, the optimization is unit economics at $0.001/call. If a feature requires charging more or settling slower, it is out of scope until that constraint changes.

What it is not

• Not a Stripe replacement. Stripe is right for subscriptions and human-on-both-sides commerce. Use both.
• Not an LLM observability tool. Layer Helicone / Langfuse / etc on top.
• Not a routing reliability product. Layer Portkey or LiteLLM on top.
• Not custodial in the "we hold your funds for months" sense — top up small amounts, withdraw when you want, treasury is public on Basescan.

Public links

• Code: github.com/spawnpay/sdk (MIT for SDK + MCP + examples)
• npm SDK: spawnpay-paywall
• npm MCP: spawnpay-mcp
• Live stats: /stats
• OpenAPI spec: /openapi.json
• llms.txt: /llms.txt (for AI crawlers)
• Treasury: 0xef1a…0161