Otto x402 Storefront

curl -s https://x402.ottoai.services/openapi.json | jq '.paths | length'

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x402 V2 Features

curl -sD - -o /dev/null https://x402.ottoai.services/crypto-news \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' \
  | base64 -d | jq '.extensions | keys'

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Which client can actually pay

• Browsing every service grouped by capability tag, with its price and its parameter.
• Inspecting a route and generating a request URL for it.
• Copying a ready-made curl command to run in your own terminal or agent.
• “Try”, which opens the raw endpoint URL in a new tab. That returns the 402 challenge — it does not pay, and it does not return data.

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Pricing Overview

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How to Make a Request (x402 V2 Flow)

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Step 1: Initial Request (Fails with 402)

curl -i "https://x402.ottoai.services/crypto-news"

HTTP/2 402
content-type: application/json; charset=utf-8
payment-required: eyJ4NDAyVmVyc2lvbiI6Mi4uLg==     ← base64-encoded payment options
access-control-expose-headers: PAYMENT-RESPONSE,PAYMENT-REQUIRED,PAYMENT-SIGNATURE,...

curl -sD - -o /dev/null "https://x402.ottoai.services/crypto-news" \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' \
  | base64 -d | jq '.accepts[] | {network, amount, asset, payTo, method: .extra.assetTransferMethod}'

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Step 2: Client Signs & Pays

1. USDC on Base (EIP-3009) — zero-approval, default for most clients
2. Any ERC-20 on Base/Polygon (Permit2) — requires Permit2 approval
3. USDC on Solana — SPL token transfer

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Step 3: Retry Request with Payment Header

curl "https://x402.ottoai.services/crypto-news" \
     -H "PAYMENT-SIGNATURE: eyJ4NDAy..."   # base64-encoded signed payment payload

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Step 4: Success (Receives Data + Receipt)

HTTP/2 200
payment-response: eyJ...              ← settlement envelope; carries the
                                        otto-content-receipt on EVM settlements
content-type: application/json; charset=utf-8

{
  "status": "success",
  "data": { "report": "Latest crypto news..." }
}

curl -sD - -o /dev/null "https://x402.ottoai.services/crypto-news" \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' \
  | base64 -d | jq '.extensions.bazaar.info.output.example'

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Step 5 (Optional): Sign-in-with-X for Repeat Access

curl -sD - -o /dev/null "https://x402.ottoai.services/crypto-news" \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' \
  | base64 -d | jq '.extensions | has("sign-in-with-x")'

curl -sD - -o /dev/null "https://x402.ottoai.services/crypto-news" \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' \
  | base64 -d | jq '.extensions."sign-in-with-x" | {info, supportedChains}'

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Understanding the Facilitator

1. Validates Payment Signatures: Verifies the PAYMENT-SIGNATURE header is cryptographically valid.
2. Prevents Replay Attacks: Tracks nonces and timestamps to prevent signature reuse.
3. Executes On-Chain Settlement: Submits transactions to Base, Polygon, or Solana to transfer the asset named in the challenge.

• A route’s accepts array is the definitive list of networks that route takes. Networks in play across the storefront are Base (eip155:8453), Polygon (eip155:137) and Solana mainnet (solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp), but not every route offers all three — some execution routes are EVM-only. Read the array; do not assume Solana is on the menu.
• Each EVM network appears twice — once for EIP-3009 (zero-approval) and once with "assetTransferMethod": "permit2".
• Each accepts entry carries maxTimeoutSeconds, and the matching signed offer carries a validUntil timestamp. Treat those two as the authority on how long you have to settle — decode them from the challenge you were served rather than assuming a fixed window.

curl -sD - -o /dev/null "https://x402.ottoai.services/crypto-news" \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' \
  | base64 -d | jq '{timeout: .accepts[0].maxTimeoutSeconds,
                     validUntil: .extensions."offer-receipt".info.offers[0].payload.validUntil}'

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Client-Side Example

npm install @x402/axios @x402/evm axios viem

import { wrapAxiosWithPayment, x402Client } from '@x402/axios';
import { ExactEvmScheme } from '@x402/evm/exact/client';
import { toClientEvmSigner } from '@x402/evm';
import axios from 'axios';
import { createPublicClient, http } from 'viem';
import { base } from 'viem/chains';
import { privateKeyToAccount } from 'viem/accounts';

// SECURITY WARNING: Never hardcode private keys in your source code!
const account = privateKeyToAccount(process.env.PRIVATE_KEY as `0x${string}`);
const publicClient = createPublicClient({ chain: base, transport: http() });
const signer = toClientEvmSigner(account, publicClient);

// Create x402 V2 client
const client = new x402Client();
client.register('eip155:*', new ExactEvmScheme(signer));

const api = wrapAxiosWithPayment(
  axios.create({ baseURL: 'https://x402.ottoai.services' }),
  client
);

// Automatic payment — the SDK handles 402 → sign → retry
const response = await api.get('/crypto-news');
console.log(response.data);

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API Endpoint Reference

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Deprecated Endpoints

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Troubleshooting - Common Issues and Solutions

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Issue: I opened the URL in my browser and got a JSON error, not data

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Issue: I passed a parameter and still got a 402

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Issue: “Payment verification failed”

• Insufficient balance of the asset named in the challenge, on the network you chose
• The signed offer you paid against has passed its validUntil
• Invalid or corrupted payment signature
• Payment already used (replay protection)

• Check your balance of the exact asset from the challenge on the exact network you selected — the challenge names both
• Ensure your system clock is synchronized (NTP)
• Re-fetch the challenge, regenerate the payment signature against the fresh offer, and retry
• Do not reuse an old payment signature

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Issue: “Invalid symbol parameter”

• Token symbol doesn’t exist or is misspelled
• Using the full token name instead of the symbol (e.g. “Bitcoin” instead of “BTC”)

• Use standard uppercase symbols: BTC, ETH, SOL
• Symbol-based routes resolve a ticker to the top-market-cap asset matching it, so a ticker shared by several tokens resolves to the largest one. Pass a chain:contract address instead where the route accepts one
• The per-route parameter and its accepted form are documented in /llm.txt

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Still Having Issues?

1. Read the error body. Unpaid 402 responses and error responses carry a hint field explaining what the endpoint wants.
2. Re-read the route in /llm.txt. It is regenerated from the running service, so it is ahead of any hand-written page.
3. Contact us — admin@useotto.xyz, or @useOttoAI. Email and social are free; feature requests welcome.

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On-Chain Standards

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ERC-8004: Agent Identity on Ethereum Mainnet

# ownerOf(6817) — selector 0x6352211e, agent ID left-padded to 32 bytes
curl -s -X POST https://ethereum-rpc.publicnode.com \
  -H 'Content-Type: application/json' \
  -d '{"jsonrpc":"2.0","id":1,"method":"eth_call","params":[{
        "to":"0x8004A169FB4a3325136EB29fA0ceB6D2e539a432",
        "data":"0x6352211e0000000000000000000000000000000000000000000000000000000000001aa1"
      },"latest"]}'

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After You Pay: Receipts and Refunds

• It is EVM-only. The v1 receipt is an EIP-712 object and needs an eip155 chain, so a call settled on Solana returns no content receipt. Pay on Base or Polygon if you need one.
• It is best-effort, and deliberately so. Receipt generation never blocks your paid response: if signing cannot complete, you still get the data you paid for, without the header. Treat the receipt as present-when-it-can-be, not as a guarantee on every 200.

curl -sD - -o /dev/null "https://x402.ottoai.services/crypto-news" \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' \
  | base64 -d | jq '.extensions | has("otto-content-receipt")'

curl -i -X POST "https://x402.ottoai.services/feedback"
# → HTTP/2 402, with the price and payment options in the PAYMENT-REQUIRED header

• It covers Otto’s own recommended services and Full Auto (see Otto X402 Router). It does not cover third-party CDP Bazaar picks — there is no Otto receipt to verify against those.
• A refund claim needs a reason of at least 50 words.
• Refunds pay only to the original payer, and never more than that payer actually paid Otto.
• They are capped at $0.01 per transaction and 10 claims per wallet per day.
• Otto grades these claims itself. It is a service-quality guarantee from a counterparty, not an independent verdict, and an approved claim is reserved rather than paid out automatically.

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ERC-8183: Agentic Commerce

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Additional Resources

• Machine-readable catalog: https://x402.ottoai.services/llm.txt
• OpenAPI document: https://x402.ottoai.services/openapi.json
• x402 discovery document: https://x402.ottoai.services/.well-known/x402
• ERC-8004 registration index: https://useotto.xyz/.well-known/erc8004/index.json

• x402 Protocol Specification: https://x402.gitbook.io/x402
• Coinbase x402 Documentation: https://docs.cdp.coinbase.com/x402/welcome
• ERC-8004 (Trustless Agents): https://eips.ethereum.org/EIPS/eip-8004
• ERC-8183 (Agentic Commerce, Draft): https://eips.ethereum.org/EIPS/eip-8183