Sleuth AI is an on-chain investigation / blockchain-forensics API. POST a JSON body to any /api/v1/* route; without a payment header you receive a 402 carrying the required USDC amount (Base) and the x402 challenge, then pay and retry. Capabilities: investigate a token's holders (whales-intel, holder-distribution, holders-overlap) and its earliest buyers + insider cohort (token-early-birds-intel); surface the known entities among a token's top holders (doxx-top-token-holders); measure trading profit and loss — a token's biggest winners and losers (top-token-traders) or one wallet's realized/unrealized PnL on one token (wallet-token-pnl); deanonymize or locate wallets (doxx-wallet, find-wallet, find-side-wallets) and expand a wallet's deep multi-hop side-wallet network (deep-side-wallet-expansion); trace funding (funding-chain-trace) and dev sells (dev-sell-check); explain a transaction (transaction-inspect); snapshot holdings (wallet-holdings); vet a shilled X post (detect-pump-and-dump-on-social-signal); or ask any free-form question (ask-me-anything) or run a full investigation with structured evidence when data is found (run-investigation). Every route takes an optional `chain` (auto | base | ethereum | arbitrum | polygon | bsc | bnb | robinhood | robinhoodchain | solana; default auto — bnb and robinhoodchain are aliases of bsc and robinhood) and an optional `conversation_id` (a UUID; reuse the same UUID across calls to continue one session and sequence turns — non-UUID values are ignored and the call runs one-shot). Covers Base, Ethereum, Arbitrum, Polygon, BNB Chain, Robinhood Chain, and Solana. FREE TIER for $SLEUTH holders: a wallet holding at least 99,000,000 SLEUTH on Base (token 0x08512BC3570d2E9015a60866d1f6941A31576Ba3) gets EVERY endpoint free — on a 402, sign the sign-in-with-x challenge (the 402's extensions['sign-in-with-x']) with that wallet's own key (EOA/eip191 signatures only; smart-contract wallets are not supported for the proof) and retry with the SIGN-IN-WITH-X header; qualifying wallets run the call with no payment. The balance is re-checked live (~60s cache) and there is a per-wallet daily free-call cap. Paying USDC via x402 is unchanged and always available on both rails; the Solana rail is payment-only (USDC — there is no SLEUTH option on Solana). Machine-readable free-tier terms: GET /api/free-tier. RESPONSE TIMES — every call is SYNCHRONOUS: the investigation runs inside the one HTTP request and the answer is the response body; there is no polling, job id, callback, or streaming. A typical investigation takes 2-3 minutes (production p50 ~140s, p75 ~180s, p90 ~250s); short factual answers come back in seconds. Hard ceiling: a call still running at 270s is aborted and returns 504 — a non-2xx never settles, so a timed-out call is not charged and may be retried (a retry often completes faster on warm data). Set your client's read/socket timeout to at least 300s (the x402 payment-authorization window is a fixed 300s) and do NOT retry before then — an early retry abandons a run that is still in flight and costs a second payment. These are observed typicals, not a guaranteed SLA; the machine-readable form is info['x-response-time'] in GET /openapi.json.