{"uid":"cap_rDpV1cq27PaERN5Dh9sav","slug":"delx-selector-extract-ddbf62a3","name":"Delx Selector Extract","description":"Extract the 4-byte function selector from calldata hex — call when reading the 4-byte selector from calldata. Use for chain input hygiene without live RPC—adjacent to OneSource-class small chain reads, but static/local only so rights and margin stay clear. Returns deterministic machine-readable JSON for $0.003 USDC via x402 on Base. Execution is first-party, local-only, stateless, and memory-only with no paid upstream, no input retention, and no claim of live chain tip, web search, or media gen…","url":"https://api.delx.ai/api/v1/x402/selector-extract","method":"POST","headers":{},"bodySchema":{"type":"object","properties":{"calldata":{"type":"string","description":"Transaction calldata hex; first 4 bytes are the selector."}}},"responseSchema":{"type":"json","example":{"valid":true,"schema":"delx/util-selector-extract/v1","selector":"0xa9059cbb","remaining_bytes":32}},"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.003","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":"$0.003/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.003","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.003","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_nOorDzo7cCeNtZLnoCtDF","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.003","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Extracts the 4-byte function selector from Ethereum transaction calldata hex, returning deterministic results with no live RPC required.","exampleAgentPrompt":"Extract the 4-byte function selector from this calldata hex: 0xa9059cbb000000000000000000000000abcdef1234567890abcdef1234567890abcdef120000000000000000000000000000000000000000000000000de0b6b3a7640000","exampleUseCases":[{"title":"Decode calldata in transaction pipeline","prompt":"I have this raw calldata hex from a transaction and I need to pull out the 4-byte function selector to figure out which contract method was invoked: 0x23b872dd000000000000000000000000abc123..."},{"title":"Input hygiene before contract simulation","prompt":"Before I pass this calldata to the simulator, can you extract the function selector so I can verify it matches the expected transferFrom method? Calldata is: 0x23b872dd00000000000000000000000012345678..."},{"title":"ABI routing from raw calldata","prompt":"I'm building a calldata router and need to extract the selector from this hex blob to decide which ABI to use for decoding: 0x70a08231000000000000000000000000deadbeef..."}],"resultDescription":"Returns deterministic JSON containing the extracted 4-byte function selector parsed from the first 4 bytes of the provided calldata hex string. No live chain data is queried; output is purely computed from the input.","failureModes":["Calldata hex is too short to contain a 4-byte selector (less than 8 hex characters after 0x prefix)","Invalid or malformed hex input returns an error","Missing calldata field in request body causes a validation error","Hex string without 0x prefix may cause parsing issues"],"whenToPreferThis":"Choose this endpoint when you need to extract a function selector from calldata locally, deterministically, and without any live RPC calls or network chain access. Ideal for input hygiene pipelines, pre-simulation validation, and ABI routing logic where you want a cheap, stateless, zero-latency decode step. Prefer over any RPC-based decode when you have raw calldata in hand and just need the selector bytes.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-09-14T12:32:41.068Z","isFirstParty":false}