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Name

Kairostamp

Tagline51/60 chars

Pay-per-call web evidence API for autonomous agents

Short description124/160 chars

Kairostamp: 0 pay-per-call web evidence endpoints for agents. x402 exact test USDC on Base-sepolia, no accounts or API keys.

Directory blurb269/280 chars

Kairostamp is a machine-to-machine web evidence API. An agent calls an endpoint, gets a 402 with x402 payment terms, pays exact test USDC on Base-sepolia, and receives the result plus a time-stamped, hash-chained receipt it can verify later. 0 endpoints at see the 402…

Medium description320/500 chars

Kairostamp is a machine-to-machine web evidence API. An agent calls an endpoint, gets a 402 with x402 payment terms, pays exact test USDC on Base-sepolia, and receives the result plus a time-stamped, hash-chained receipt it can verify later. 0 endpoints at see the 402 challenge. No signup, no API keys, no subscription.

Long description

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. Payment is x402 version 2, scheme "exact", test USDC on Base-sepolia. 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. Endpoints (0): . Pricing: see the 402 challenge. Every 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. Machine-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.

Pricing

see the 402 challenge, x402 exact test USDC on Base-sepolia. No subscription.

Authentication

None. Payment replaces authentication (x402 v2, scheme exact).

Primary category

Developer tools / Agent tools / Web data

Contact

support@kairostamp.com

Categories and keywords

Keywords

x402, pay per call api, agent tools, web evidence, url snapshot, tamper evident receipt, usdc, base, no api key

Links

All links

Homepage:https://kairostamp.com
Documentation:https://kairostamp.com/docs
OpenAPI 3.1:https://kairostamp.com/openapi.jsonmachine
Agent card:https://kairostamp.com/.well-known/agent-card.jsonmachine
x402 resource index:https://kairostamp.com/.well-known/x402machine
llms.txt:https://kairostamp.com/llms.txtmachine
Discovery document:https://kairostamp.com/api/public/discoverymachine
Offer catalog:https://kairostamp.com/api/public/offersmachine
Discovery status:https://kairostamp.com/api/public/discovery-statusmachine
Listing kit (JSON):https://kairostamp.com/listing-kit.jsonmachine
Terms:https://kairostamp.com/terms
Privacy:https://kairostamp.com/privacy

Endpoint table

Endpoint	Method	Price

Snippets

See the payment terms (free, spends nothing)

curl -i "https://kairostamp.com/api/public/discovery"

Fetch the machine-readable descriptors

curl -s https://kairostamp.com/.well-known/agent-card.json
curl -s https://kairostamp.com/openapi.json
curl -s https://kairostamp.com/llms.txt

Markdown listing line (awesome-lists, README tables)

- [Kairostamp](https://kairostamp.com) — Kairostamp: 0 pay-per-call web evidence endpoints for agents. x402 exact test USDC on Base-sepolia, no accounts or API keys.

Where this goes

x402 Bazaar (Coinbase CDP discovery index)automatic
Consumes 402 challenge + one settled mainnet payment per route. No form exists. A route is indexed after it validates and takes one settled mainnet payment. Verified with scripts/index-pass.mjs.
x402 clients probing /.well-known/x402automatic
Consumes /.well-known/x402. Served on every request; needs no submission at all.
Agent frameworks reading agent cardsautomatic
Consumes /.well-known/agent-card.json. Advertises tools, input schemas, pricing and authentication: none.
LLM crawlers and RAG pipelinesautomatic
Consumes /llms.txt, /openapi.json, sitemap.xml. robots.txt allows all discovery paths; the sitemap lists them.
OpenAPI-consuming tool buildersautomatic
Consumes /openapi.json. 402 documented per operation so a generated client knows to pay and retry.
GitHub awesome-lists and README tablesmanual
Consumes markdown_listing snippet. Needs a pull request from a GitHub account. Copy is pre-written above.
API and agent-tool directories with signup formsself-serve
Consumes fields + links. Each form field here is already sized to the usual limits. Paste, no writing required.

Listing kit