{"uid":"cap_Sw_6jb18Q4CyiyRGKSW5J","slug":"fairseal-payload-hash-anchoring-base-mainnet-33b917d4","name":"FairSeal Payload Hash Anchoring (Base Mainnet)","description":"Anchor a SHA-256 payload hash (64 lowercase hex chars) into a Merkle batch on Base mainnet. Payment: $0.001 USDC per submission (batch-settled). Returns anchor_id (202); poll status_url for Merkle proof + on-chain tx hash.","url":"https://x402.fairseal.io/v2/anchor?utm_source=zero.xyz","method":"POST","headers":{},"bodySchema":{"type":"object","properties":{"tier":{"enum":["batch"],"type":"string","description":"batch (default, ~60s). realtime requires a pro API key and is not available via x402."},"metadata":{"type":"object","description":"Optional metadata (max 1KB). Stored with receipt."},"payload_hash":{"type":"string","pattern":"^[0-9a-f]{64}$","description":"SHA-256 hex of content to anchor (64 lowercase hex chars)"}}},"responseSchema":null,"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_eRS4FLJoIAFHMy_HxTbeC","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":"Anchors a SHA-256 payload hash into a Merkle batch on Base mainnet, returning an anchor ID and a polling URL for the resulting on-chain proof.","exampleAgentPrompt":"Anchor the SHA-256 hash a3f1e2b4c5d6789012345678abcdef01234567890abcdef1234567890abcdef12 to Base mainnet using the batch tier — I want a Merkle proof and on-chain transaction hash I can poll for later.","exampleUseCases":[{"title":"Document provenance timestamping","prompt":"I have a SHA-256 hash of a legal contract: b7e3c2a1f09d8456780123456789abcdef0123456789abcdef0123456789abcd. Anchor it to Base mainnet in batch mode so I have on-chain proof of when it existed."},{"title":"AI output integrity verification","prompt":"We just generated an AI model report and its hash is 9f2d1c4e5a7b8903456789abcdef012345678901abcdef234567890123456789 — anchor it on Base mainnet with batch tier and tag it with metadata noting it's an AI audit record."},{"title":"Software release notarization","prompt":"Before shipping this release, anchor the SHA-256 digest of our build artifact — d4c3b2a1e0f9876543210fedcba9876543210fedcba9876543210fedcba987654 — to Base mainnet so we have immutable proof of what code shipped and when."}],"resultDescription":"Returns HTTP 202 with an anchor_id and a status_url. Polling the status_url later yields the completed Merkle proof (the hash's inclusion proof within the batch) and the on-chain transaction hash on Base mainnet confirming the batch settlement.","failureModes":["Invalid payload_hash format (not 64 lowercase hex chars) returns 400 validation error","realtime tier requested without a valid pro API key returns 403 forbidden","metadata exceeds 1KB limit returns 400 payload too large","Payment not fulfilled via x402 protocol returns 402 Payment Required","Polling status_url before batch settles returns pending status (batch settles ~60s)","Network or Base mainnet congestion may delay on-chain confirmation beyond expected ~60s window"],"whenToPreferThis":"Choose this endpoint when you need cheap ($0.001 USDC), blockchain-anchored proof of existence for a SHA-256 hash on Base mainnet with Merkle batch efficiency. Prefer batch tier for cost-sensitive high-volume anchoring; use realtime tier only when you need an immediate on-chain commitment. This is ideal for document notarization, AI output auditing, software release provenance, and compliance evidence where you need a verifiable, tamper-proof timestamp without storing the raw content on-chain.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-21T12:34:48.157Z","isFirstParty":false,"canonicalSlug":"fairseal-payload-hash-anchoring-base-mainnet-33b917d4"}