{"uid":"cap_aDr9Hy2M5yrQ2-K9MTrDb","slug":"keystone-opportunity-api-base-wallet-lookup-0667ccfc","name":"Keystone Opportunity API – Base Wallet Lookup","description":"Low-cost, deterministic x402 utilities for autonomous agents on Base. Every /v1 route is priced in USDC and settles onchain via the x402 protocol; discover and pay programmatically through the x402 Bazaar. No API keys, no subscriptions.","url":"https://keystone-opportunity-api.keystone-opportunity.workers.dev/v1/base/wallet/%7Baddress%7D","method":"GET","headers":{},"bodySchema":{"type":"object","properties":{"properties":{"type":"string"}}},"responseSchema":{"type":"json","example":{"eth":0.0123,"usdc":4.77,"address":"0x0000000000000000000000000000000000000000","chainId":8453,"network":"base","contract":false,"observedAt":"2026-07-26T00:00:00.000Z","transactionCount":12}},"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.02","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.02/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.02","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.02","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_P2PYrM5e7Fv0BIpBK-1ZM","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.02","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Fetches ETH and USDC balances, transaction count, and contract status for a given Base network wallet address, paid via x402/USDC onchain.","exampleAgentPrompt":"What are the current ETH and USDC balances for the Base wallet 0x1234567890abcdef1234567890abcdef12345678, and is it a contract address?","exampleUseCases":[{"title":"DeFi portfolio balance check","prompt":"Can you pull the current ETH and USDC balances for my Base wallet 0xAbC1234567890abcdef1234567890abcdef12345 and tell me how many transactions it's made?"},{"title":"Contract vs EOA verification","prompt":"I need to know whether the Base address 0xdEaD000000000000000042069420694206942069 is a smart contract or a regular wallet — can you check?"},{"title":"Autonomous agent treasury audit","prompt":"Check the ETH and USDC holdings for the agent treasury wallet 0xBEEF000000000000000000000000000000000001 on Base so I can decide if it needs a top-up."}],"resultDescription":"Returns a JSON object containing the wallet's ETH balance (float), USDC balance (float), the queried address, chain ID (8453 for Base), network name ('base'), a boolean indicating whether the address is a smart contract, the transaction count, and the timestamp of observation.","failureModes":["Invalid or malformed wallet address returns an error or empty result","Address not yet active on Base (zero transactions) may return zeroed balances","Network congestion or RPC issues may cause stale or delayed data","x402 payment failure (insufficient USDC, wrong facilitator) blocks the request","Cloudflare Worker timeout on high-load periods"],"whenToPreferThis":"Choose this endpoint when you need a fast, no-API-key, onchain-settled lookup of ETH and USDC balances plus contract/EOA status for a Base network address. Ideal for autonomous agents that already operate within the x402 payment ecosystem and need deterministic, programmatic wallet data without managing API subscriptions.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-09-13T06:30:35.218Z","isFirstParty":false}