{"id":"cmp16xhp2000bs601hvgaodko","url":"https://api.loomal.ai/h/ethereum-whitepaper","method":"GET","title":"Ethereum Whitepaper","description":null,"category":"Crypto, Ethereum","price":{"amountUsdc":"0.10","network":"base"},"x402":{"challenge":"https://api.loomal.ai/v0/payments/challenge"},"addedAt":"2026-05-11T12:41:14.966Z","instructions":{"format":"markdown","body":"# Ethereum Whitepaper\n\n\n\n## How to call this endpoint\n\nThis is a paid HTTP API. You pay per call in USDC over the open x402 protocol.\n\n### Step 1 — Get the payment requirement\n\nSend a request to the endpoint URL. The first call returns HTTP 402 with a JSON body describing the payment.\n\n```\nGET https://api.loomal.ai/h/ethereum-whitepaper\n```\n\nThe 402 response body has shape:\n```json\n{\n  \"x402Version\": 1,\n  \"accepts\": [\n    {\n      \"scheme\": \"exact\",\n      \"network\": \"base\",\n      \"maxAmountRequired\": \"<raw USDC amount>\",\n      \"resource\": \"https://api.loomal.ai/h/ethereum-whitepaper\",\n      \"mimeType\": \"<content type you'll get on settle>\",\n      \"payTo\": \"<seller wallet>\",\n      \"asset\": \"<USDC contract address>\",\n      \"extra\": { \"name\": \"USD Coin\", \"version\": \"2\" }\n    }\n  ]\n}\n```\n\n### Step 2 — Sign the payment\n\nTake `accepts[0]` from the 402 body. Sign an EIP-3009 `transferWithAuthorization` for the listed `maxAmountRequired` to `payTo` on the listed network. Base64-encode the signed payload (the full `{x402Version, scheme, network, payload}` envelope per the x402 spec).\n\nYou can do this with any wallet that supports x402, or via the Loomal SDK in any language.\n\n### Step 3 — Retry with the X-Payment header\n\nSend the same request again, this time with your encoded payment in the `X-Payment` header:\n\n```\nGET https://api.loomal.ai/h/ethereum-whitepaper\nX-Payment: <base64-encoded-payment-envelope>\n```\n\nLoomal verifies the signature, settles on-chain (~2 seconds), and returns the configured response. The `X-Payment-Response` header on the success response contains the settled transaction hash.\n\n## Endpoint details\n\n| | |\n|--|--|\n| URL | https://api.loomal.ai/h/ethereum-whitepaper |\n| Method | GET |\n| Price | 0.10 USDC |\n| Network | base |\n| Listed | 2026-05-11T12:41:14.966Z |\n| Tags | Crypto, Ethereum |\n| Spec | [x402 v1](https://loomal.ai/.well-known/x402-discovery.json) |\n\n## Browseable\n\nA human-friendly version of this listing lives at:\n`https://loomal.ai/discover/cmp16xhp2000bs601hvgaodko`\n"}}