AI agents hallucinate. Here is how to cryptographically notarize their output for $0.01

A solo developer built AOTrust, a service that cryptographically notarizes AI agent outputs for $0.01 per proof on Base L2. It issues a 239-byte Provenance Data Record (PDR) using the HTTP 402 payment protocol, allowing agents to prove the existence and timestamp of artifacts without uploading the actual data. The service aims to solve trust issues in autonomous agent workflows by providing an immutable audit trail.

We have a growing problem in the autonomous AI agent space: Garbage in, garbage out, and no proof of when it happened. When your AI agent generates source code, analyzes market data, or creates a financial report, how do you mathematically prove that this specific artifact was generated at a specific time? How do you prove to your clients that the output wasn't retroactively edited before a dispute? I wanted a "notary stamp" for AI agents. But existing oracle solutions are too expensive often $0.25 - $1.00+ per call and require complex smart contract integrations. So, as a solo developer, I built AOTrust . It does exactly one thing: it issues a PDR Provenance Data Record for exactly $0.01 USDC on Base L2, using the HTTP 402 protocol. A PDR is a highly optimized 239-byte cryptographic receipt. It proves that a specific digital artifact existed at a specific point in time. It contains: Privacy first: You never upload your actual artifact or AI prompt. You only send the SHA-256 hash. I designed this to be integrated into any agentic workflow Python, TS, Rust using standard HTTP requests. It uses the x402 payment protocol. Here is the entire integration in 3 steps: First, your agent hashes its output locally. import hashlib work hash = hashlib.sha256 b"your agent's JSON output" .hexdigest Step 2: Request Notarization Get a Quote Send the hash to the API. Because AOTrust is a payment-bound proof layer, the server will intentionally reject it with an HTTP 402 Payment Required status, returning the payment instructions. curl -X POST https://api.aotrust.link/notarize https://api.aotrust.link/notarize \ -H "Content-Type: application/json" \ -d '{"work hash":"YOUR SHA256 HEX"}' Response HTTP 402 : { "payTo": "0x97E9af6B...Ab8Cc800", "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913", // USDC on Base "maxAmountRequired": "10000", // $0.01 6 decimals "network": "eip155:8453", "maxTimeoutSeconds": 300 } Step 3: Pay and Get Your Proof Your agent signs an EIP-3009 transferWithAuthorization with its Ethereum wallet to authorize the $0.01 payment. Encode the signature and send it in the x-payment header. curl -X POST https://api.aotrust.link/notarize https://api.aotrust.link/notarize \ -H "Content-Type: application/json" \ -H "x-payment: YOUR BASE64URL ENCODED SIGNATURE" \ -d '{"work hash":"YOUR SHA256 HEX"}' Response HTTP 200 : { "job id": "550e8400-e29b-41d4-a716-446655440000", "pdr b64": "AwEFA1kuagAAAABub3...", "payment anchor type": "X402 BASE" } Boom. You just received your 239-byte cryptographic proof pdr b64 . Verifying the Proof You can pass this job id or the raw base64 string to your clients or users. Anyone can verify the cryptographic seal instantly without an account, API keys, or paying any fees: verify.aotrust.link Why build this? If you are building autonomous agents, integrating them into marketplaces, or generating automated financial/audit reports, trust is your biggest bottleneck. By appending an AOTrust PDR to your agent's deliverable, you give your clients an un-fakable, third-party verified timestamp of the work. I’m currently running the mainnet infrastructure. If you are building agentic workflows and need an immutable audit trail, I’d love to hear your thoughts on this API flow Docs: docs.aotrust.link GitHub Specs & Parser : github.com/GitSerge-crypto/aotrust-skills