Free x402 payment-challenge generator with Express/Hono snippets; paid tier adds more frameworks.
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Build a spec-compliant x402 v2 payment challenge (402 response body) from a price, wallet and network. Returns the challenge JSON, the base64 PAYMENT-REQUIRED header value, a curl test command, and free code snippets (Cloudflare Worker, Express) to return it. Free, no auth. Pre-validated: the same shape checks x402lint.js runs on existing endpoints.
Price in whole USDC, e.g. '0.02'.
0x-prefixed EVM wallet address to receive payment.
Token contract address, default USDC on Base.
x402 network id, default 'base'.
The URL this challenge is for, default a placeholder.
Human description of what's being sold.
Pick your client. Values in capitals, like YOUR_TOKEN, are yours to fill in.
Run in a terminal
claude mcp add --transport http tools https://x402gen.sebastiaan-ba3.workers.dev/mcp
Build a spec-compliant x402 v2 payment challenge (402 response body) from a price, wallet and network. Returns the challenge JSON, the base64 PAYMENT-REQUIRED header value, a curl test command, and free code snippets (Cloudflare Worker, Express) to return it. Free, no auth. Pre-validated: the same shape checks x402lint.js runs on existing endpoints.
| Argument | Type | Description |
|---|---|---|
| asset | string | Token contract address, default USDC on Base. |
| price* | string | Price in whole USDC, e.g. '0.02'. |
| pay_to* | string | 0x-prefixed EVM wallet address to receive payment. |
| network | string | x402 network id, default 'base'. |
| resource | string | The URL this challenge is for, default a placeholder. |
| description | string | Human description of what's being sold. |
{
"type": "object",
"required": [
"price",
"pay_to"
],
"properties": {
"asset": {
"type": "string",
"description": "Token contract address, default USDC on Base."
},
"price": {
"type": "string",
"description": "Price in whole USDC, e.g. '0.02'."
},
"pay_to": {
"type": "string",
"description": "0x-prefixed EVM wallet address to receive payment."
},
"network": {
"type": "string",
"description": "x402 network id, default 'base'."
},
"resource": {
"type": "string",
"description": "The URL this challenge is for, default a placeholder."
},
"description": {
"type": "string",
"description": "Human description of what's being sold."
}
}
}Same as generate_x402_challenge plus 5 more framework snippets (FastAPI, Next.js, Django, Go, Rails, raw Node) and a ready /.well-known/x402.json manifest. Requires payment (USDC on Base, x402) -- NOT callable for free over MCP. Calling this tool returns the exact HTTP request to make instead; it does not run the generation itself.
| Argument | Type | Description |
|---|---|---|
| asset | string | Token contract address, default USDC on Base. |
| price* | string | Price in whole USDC, e.g. '0.02'. |
| pay_to* | string | 0x-prefixed EVM wallet address to receive payment. |
| network | string | x402 network id, default 'base'. |
| resource | string | The URL this challenge is for, default a placeholder. |
| description | string | Human description of what's being sold. |
{
"type": "object",
"required": [
"price",
"pay_to"
],
"properties": {
"asset": {
"type": "string",
"description": "Token contract address, default USDC on Base."
},
"price": {
"type": "string",
"description": "Price in whole USDC, e.g. '0.02'."
},
"pay_to": {
"type": "string",
"description": "0x-prefixed EVM wallet address to receive payment."
},
"network": {
"type": "string",
"description": "x402 network id, default 'base'."
},
"resource": {
"type": "string",
"description": "The URL this challenge is for, default a placeholder."
},
"description": {
"type": "string",
"description": "Human description of what's being sold."
}
}
}We read every tool's name, description and inputs the way the model will, looking for instructions hidden from you. A clean result means no warning signs, not a guarantee. Scanned Nov 12, 2026.
No readOnlyHint / destructiveHint annotations, so clients can't tell a read from a write without asking.
Fix: Add annotations to each tool, e.g. { readOnlyHint: true } for tools that only read.