{
  "id": 16289276,
  "title": "How an agent finds a paid endpoint: .well-known/x402.json, llms.txt and an MCP server card",
  "url": "https://urgent.news/2026/10/24/how-an-agent-finds-a-paid-endpoint-well-known-x402-json-llms-txt-and",
  "topic": "ai",
  "section": "AI",
  "published": "2026-10-24T06:16:02.000Z",
  "source": {
    "name": "Dev.to",
    "slug": "dev-to",
    "url": "https://dev.to/dutiful_dev/how-an-agent-finds-a-paid-endpoint-well-knownx402json-llmstxt-and-an-mcp-server-card-ec1"
  },
  "original_language": "en",
  "account": "To discover a paid endpoint, an agent must first find the discovery files and learn the payment details. The /.well-known/x402.json file contains the payment facts in a machine-readable format, outlining the resource URL, scheme, network, asset, amount, and payee. The /openapi.json file provides the full contract, payment terms, and a self-describing OpenAPI 3 specification. The /llms.txt file offers a concise summary of the payment flow for language models. Lastly, the /.well-known/mcp/server-card.json file gives MCP agents a streamable-HTTP MCP server with three tools for coverage check, order creation, and report retrieval. By providing these self-describing files, agents can explore and experiment without incurring costs, and crawlers can index the payment shape without making a real payment. These files make the service more legible and accessible to various agents, increasing the likelihood of trust in the paid endpoint.",
  "summary": "Disclosure: I build Dutiful, the service used as the example. The files below are Dutiful's own published discovery artifacts - treat them as our setup, not a specification or a guarantee that any framework supports them. A previous post ( https://dev.to/dutiful_dev/how-an-agent-pays-for-and-reads-a-company-check-over-x402-3dh3 ) walked through paying for an HTTP request with x402: create the…",
  "key_points": [
    "/.well-known/x402.json contains payment facts in machine-readable format",
    "/openapi.json provides full contract, payment terms, and OpenAPI 3 specification"
  ],
  "editors_take": "Standardizing machine-readable discovery files reduces friction for autonomous agents, allowing them to navigate payment structures and service contracts without incurring costs or requiring manual human intervention.",
  "illustration": null,
  "coverage": {
    "outlets": 1,
    "also_reported_by": []
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}