One-time licenses instead of per-call fees: shipping a paid MCP server with x402

说明与用途

作者使用x402和Base主网实现了一个一次性许可证的MCP服务器，取代了按调用计费，简化了每天使用几次工具的支付流程。

问题

Per-call billing for MCP servers creates a subscription‑like experience for tools used a few times a day, making micropayments cumbersome.

结果

The MCP server successfully implements a one‑time license model, reducing payment friction for users and demonstrating that x402 can support license‑based billing.

工作流

• 1. Client requests /api/comprar and receives a 402 response with payment details.
• 2. Client pays via an x402‑capable facilitator and retries with an X-PAYMENT header.
• 3. Server verifies payment, mints a license token, and returns it in a JSON response.
• 4. Client includes the x-license header on subsequent MCP calls.
• 5. Server validates the license hash stored in KV and enforces a 200‑call/month limit per license.

证据

Everyone writing about paid MCP servers right now is charging per call.

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a one-time 5 USDC payment on Base mainnet.

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The license travels as a plain header on every MCP call: x-license: ct_...

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Store only the hash. The KV namespace never sees the license token, only sha256(token).

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Cap heavy buyers in the product, not in the contract. 200 calls per month per license.

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