{"uid":"cap_GN7Zby1W6vu1MXnOVGXe5","slug":"skills-onesource-io-286637b6","name":"Ethereum Chain ID Lookup (EIP-155)","description":"Ethereum chain ID (EIP-155) via eth_chainId - confirm which chain a network is on","url":"https://skills.onesource.io/api/chain/chain-id","method":"GET","headers":{},"bodySchema":{"type":"object","properties":{"network":{"enum":["ethereum","sepolia","avax","megaeth","megaeth-testnet","base"],"type":"string","default":"ethereum"}}},"responseSchema":{"type":"object","required":["data","meta"],"properties":{"data":{"type":"object","required":["result"],"properties":{"result":{"type":"string"}}},"meta":{"type":"object","required":["endpoint","request_id"],"properties":{"endpoint":{"type":"string"},"request_id":{"type":"string"}}}}},"example":{"request":{"network":"ethereum"},"response":{"data":{"result":"0x1"},"meta":{"endpoint":"/api/chain/chain-id","request_id":"47c519afe50ef13d"}}},"exampleRequest":{"network":"ethereum"},"tags":["x402"],"displayCostAmount":"0.001","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"settled","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":"$0.001/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.001","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.001","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_dcAGeY-Wvhh7w2oJ1P0AB","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.001","costPer":"request","priority":0,"asset":null,"unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Returns the EIP-155 chain ID for a specified Ethereum-compatible network via eth_chainId","exampleAgentPrompt":"What is the EIP-155 chain ID for the Ethereum mainnet? Also check what it returns for Base and Sepolia.","exampleUseCases":[{"title":"Validate chain before wallet configuration","prompt":"Before I set up my wallet to connect to the Avalanche network, can you confirm what the EIP-155 chain ID is? I want to make sure I'm configuring it correctly."},{"title":"Verify chain ID for transaction signing","prompt":"I'm about to sign a transaction on MegaETH testnet. Can you quickly verify the chain ID I should be using so I don't accidentally sign on the wrong network?"},{"title":"Cross-chain operation verification","prompt":"I'm building a bridge tool that works across multiple networks. Can you get me the chain IDs for Ethereum mainnet, Arbitrum, and Polygon so I can validate user transactions across all three chains?"}],"resultDescription":"Returns a hex-encoded chain ID (e.g. '0x1' for Ethereum mainnet) for the specified network, along with request metadata including the endpoint path and a unique request ID.","failureModes":["Invalid network name returns error — only 'ethereum', 'sepolia', 'avax', 'megaeth', 'megaeth-testnet', 'base' are supported","Missing network parameter defaults to 'ethereum'","Network RPC node unavailable may return a 500 or timeout","Payment failure (insufficient x402 balance) blocks the request"],"whenToPreferThis":"Use this endpoint when you need to programmatically confirm which EIP-155 chain ID corresponds to a supported EVM network before signing transactions, configuring wallets, or validating cross-chain operations. Prefer this over manual lookups when working with multiple networks including testnets like Sepolia or MegaETH.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-09-14T00:40:13.632Z","isFirstParty":false}