{"generated_at":"2026-08-23T18:07:07.414Z","base_url":"https://kairostamp.com","name":"Kairostamp","fields":[{"key":"name","label":"Name","value":"Kairostamp"},{"key":"tagline","label":"Tagline","limit":60,"value":"Pay-per-call web evidence API for autonomous agents"},{"key":"short_description","label":"Short description","limit":160,"value":"Kairostamp: 10 pay-per-call web evidence endpoints for agents. x402 exact USDC on Base mainnet, no accounts or API keys."},{"key":"tweet","label":"Directory blurb","limit":280,"value":"Kairostamp is a machine-to-machine web evidence API. An agent calls an endpoint, gets a 402 with x402 payment terms, pays exact USDC on Base mainnet, and receives the result plus a time-stamped, hash-chained receipt it can verify later. 10 endpoints at $0.005–$0.020 per call…"},{"key":"medium_description","label":"Medium description","limit":500,"value":"Kairostamp is a machine-to-machine web evidence API. An agent calls an endpoint, gets a 402 with x402 payment terms, pays exact USDC on Base mainnet, and receives the result plus a time-stamped, hash-chained receipt it can verify later. 10 endpoints at $0.005–$0.020 per call. No signup, no API keys, no subscription."},{"key":"long_description","label":"Long description","value":"Paid machine-to-machine web evidence API. Fetches one public http/https URL server-side and returns a time-stamped, tamper-evident receipt; the change-check endpoint also compares it against a caller-supplied baseline.\n\nPayment is x402 version 2, scheme \"exact\", USDC on Base mainnet. A compliant client negotiates payment automatically from the 402 response — there is no account, no API key and no subscription; the agent's wallet is the account.\n\nEndpoints (10): snapshot, change-check, digest, headers, verify, robots-check, redirect-audit, text-extract, link-map, sitemap. Pricing: $0.005–$0.020 per call.\n\nEvery paid call writes to an append-only, hash-chained evidence log and returns a receipt id that can be re-verified later. Order of operations is verify payment, fetch, then settle, so a failed fetch is not charged. Fetching runs in an isolated, IP-pinned service: http/https only, private ranges blocked, DNS pinned against rebinding, 3 redirects maximum, 10 second deadline and a 1 MiB body cap.\n\nMachine-readable descriptors: OpenAPI 3.1 at https://kairostamp.com/openapi.json, an agent card at https://kairostamp.com/.well-known/agent-card.json, an x402 resource index at https://kairostamp.com/.well-known/x402, and a plain-text index at https://kairostamp.com/llms.txt."},{"key":"pricing","label":"Pricing","value":"$0.005–$0.020 per call, x402 exact USDC on Base mainnet. No subscription."},{"key":"authentication","label":"Authentication","value":"None. Payment replaces authentication (x402 v2, scheme exact)."},{"key":"category","label":"Primary category","value":"Developer tools / Agent tools / Web data"},{"key":"contact","label":"Contact","value":"support@kairostamp.com"}],"categories":["Agent tools","Web data","Evidence & provenance","x402 / pay-per-call APIs"],"keywords":["x402","pay per call api","agent tools","web evidence","url snapshot","tamper evident receipt","usdc","base","no api key","snapshot","change-check","digest","headers","verify","robots-check","redirect-audit","text-extract","link-map","sitemap"],"links":[{"label":"Homepage","url":"https://kairostamp.com","machine_readable":false},{"label":"Documentation","url":"https://kairostamp.com/docs","machine_readable":false},{"label":"OpenAPI 3.1","url":"https://kairostamp.com/openapi.json","machine_readable":true},{"label":"Agent card","url":"https://kairostamp.com/.well-known/agent-card.json","machine_readable":true},{"label":"x402 resource index","url":"https://kairostamp.com/.well-known/x402","machine_readable":true},{"label":"llms.txt","url":"https://kairostamp.com/llms.txt","machine_readable":true},{"label":"Discovery document","url":"https://kairostamp.com/api/public/discovery","machine_readable":true},{"label":"Listing kit (JSON)","url":"https://kairostamp.com/listing-kit.json","machine_readable":true},{"label":"Terms","url":"https://kairostamp.com/terms","machine_readable":false},{"label":"Privacy","url":"https://kairostamp.com/privacy","machine_readable":false}],"endpoints":[{"name":"snapshot","method":"POST","url":"https://kairostamp.com/api/v1/snapshot","price":null,"summary":"Kairostamp evidence snapshot: server-side fetch of one public http/https URL, returning a time-stamped receipt with the response status, content type, byte length, SHA-256 of the body, redirect chain, a text preview, and a tamper-evident hash-chain entry"},{"name":"change_check","method":"POST","url":"https://kairostamp.com/api/v1/change-check","price":null,"summary":"Kairostamp change check: server-side fetch of one public http/https URL, compared against a baseline the caller already holds"},{"name":"digest","method":"GET","url":"https://kairostamp.com/api/v1/digest","price":"$0.01","summary":"URL digest receipt: server-side fetch of one public http/https URL, returning a time-stamped receipt with the HTTP status, final URL, content type, byte length, SHA-256 of the response body, redirect chain, receipt id and tamper-evident hash-chain entry"},{"name":"headers","method":"GET","url":"https://kairostamp.com/api/v1/headers","price":"$0.005","summary":"URL HTTP metadata receipt: server-side fetch of one public http/https URL, returning only transport metadata — HTTP status, final URL, redirect chain, content type and byte length — plus a receipt id"},{"name":"verify","method":"GET","url":"https://kairostamp.com/api/v1/verify","price":"$0.005","summary":"Receipt verification: read-only hash-chain verification of one existing Kairostamp receipt id"},{"name":"robots_check","method":"GET","url":"https://kairostamp.com/api/v1/robots-check","price":"$0.005","summary":"robots.txt check: fetches the origin's /robots.txt server-side and reports whether a given URL path is allowed or blocked for a user agent, with the matched rule, the robots URL, the HTTP status, a timestamp and a tamper-evident receipt"},{"name":"redirect_audit","method":"GET","url":"https://kairostamp.com/api/v1/redirect-audit","price":"$0.01","summary":"Redirect audit: follows one public http/https URL server-side and returns the ordered redirect chain, hop count, final URL, final HTTP status, whether the destination changed origin and whether HTTPS was downgraded to HTTP, with a timestamp and a tamper-evident receipt"},{"name":"text_extract","method":"GET","url":"https://kairostamp.com/api/v1/text-extract","price":"$0.02","summary":"Readable text extraction: fetches one public HTML page server-side and returns clean plain text with the page title, final URL, HTTP status, content type, SHA-256 of the response body, a timestamp and a tamper-evident receipt"},{"name":"link_map","method":"GET","url":"https://kairostamp.com/api/v1/link-map","price":"$0.015","summary":"Link map: fetches one public HTML page server-side and returns up to 100 normalized, deduplicated http/https links with internal/external classification and counts, the final URL, a timestamp and a tamper-evident receipt"},{"name":"sitemap","method":"GET","url":"https://kairostamp.com/api/v1/sitemap","price":"$0.01","summary":"Sitemap lookup: locates a site's sitemap from robots.txt or same-origin /sitemap.xml, fetches it server-side and returns up to 100 normalized http/https URLs with the sitemap URL, document kind, count, truncation flag, a timestamp and a tamper-evident receipt"}],"snippets":[{"key":"curl_402","label":"See the payment terms (free, spends nothing)","language":"bash","body":"curl -i \"https://kairostamp.com/api/v1/digest?url=https://example.com/\""},{"key":"curl_discovery","label":"Fetch the machine-readable descriptors","language":"bash","body":"curl -s https://kairostamp.com/.well-known/agent-card.json\ncurl -s https://kairostamp.com/openapi.json\ncurl -s https://kairostamp.com/llms.txt"},{"key":"markdown_listing","label":"Markdown listing line (awesome-lists, README tables)","language":"markdown","body":"- [Kairostamp](https://kairostamp.com) — Kairostamp: 10 pay-per-call web evidence endpoints for agents. x402 exact USDC on Base mainnet, no accounts or API keys."}],"targets":[{"name":"x402 Bazaar (Coinbase CDP discovery index)","url":"https://docs.cdp.coinbase.com/x402/seller/get-discovered","submission":"automatic","consumes":"402 challenge + one settled mainnet payment per route","note":"No form exists. A route is indexed after it validates and takes one settled mainnet payment. Verified with scripts/index-pass.mjs."},{"name":"x402 clients probing /.well-known/x402","url":"/.well-known/x402","submission":"automatic","consumes":"/.well-known/x402","note":"Served on every request; needs no submission at all."},{"name":"Agent frameworks reading agent cards","url":"/.well-known/agent-card.json","submission":"automatic","consumes":"/.well-known/agent-card.json","note":"Advertises tools, input schemas, pricing and authentication: none."},{"name":"LLM crawlers and RAG pipelines","url":"/llms.txt","submission":"automatic","consumes":"/llms.txt, /openapi.json, sitemap.xml","note":"robots.txt allows all discovery paths; the sitemap lists them."},{"name":"OpenAPI-consuming tool builders","url":"/openapi.json","submission":"automatic","consumes":"/openapi.json","note":"402 documented per operation so a generated client knows to pay and retry."},{"name":"GitHub awesome-lists and README tables","url":"https://github.com/topics/x402","submission":"manual","consumes":"markdown_listing snippet","note":"Needs a pull request from a GitHub account. Copy is pre-written above."},{"name":"API and agent-tool directories with signup forms","url":"/listing-kit.json","submission":"self-serve","consumes":"fields + links","note":"Each form field here is already sized to the usual limits. Paste, no writing required."}]}