Roundhouse AI

kairostamp.com

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. Single GET query parameter (url). One call performs one fetch; there is no monitoring and no retry.

OtherLiveeip155:8453Exactvia cdp
https://kairostamp.com/api/v1/digest
Calls · 30d
1→ 0%
This endpoint's own trailing-30-day call count, as published by the upstream catalog and snapshotted daily. 30 snapshots so far.
$0.04
Verified settled volume
11 settlements proven x402 by their on-chain EIP-3009 marker.
$0.0020
Listed price
As published in the catalog. Always read the live 402 before paying.
1
Calls · 30d
Upstream's own call count for this endpoint, not ours.
1
Unique payers · 30d
Last called 2026-08-23 09:07Z
—
Upstream on-chain volume
Reported by the source catalog.
Paid to
0xdB6F694aE695C632C82677a50593B46137808453

The wallet the 402 directs payment to. Its whole payment record — every payer, every chain — is on the merchant page.

Asset 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913

Provider

The payTo wallet does not resolve to a registered ERC-8004 agent. That is not a verdict on the service — most of the catalog is unregistered.

Live 402 challenge

Captured by the enrichment pass, not read just now. Prices can change — always read the 402 the endpoint answers with.

{
  "error": "Payment required",
  "accepts": [
    {
      "asset": "0x036CbD53842c5426634e7929541eC2318f3dCF7e",
      "extra": {
        "name": "USDC",
        "version": "2"
      },
      "payTo": "0xdB6F694aE695C632C82677a50593B46137808453",
      "amount": "10000",
      "scheme": "exact",
      "network": "eip155:84532",
      "maxTimeoutSeconds": 300
    }
  ],
  "resource": {
    "url": "https://kairostamp.com/api/v1/digest"
  },
  "extensions": {
    "builder-code": {
      "info": {
        "s": [
          "cdp_sdk_server"
        ]
      },
      "schema": {
        "type": "object",
        "$schema": "https://json-schema.org/draft/2020-12/schema",
        "properties": {
          "a": {
            "type": "string",
            "pattern": "^[a-z0-9_]{1,32}$",
            "description": "App builder code"
          },
          "s": {
            "type": "array",
            "items": {
              "type": "string",
              "pattern": "^[a-z0-9_]{1,32}$"
            },
            "maxItems": 11,
            "description": "Service builder codes"
          },
          "w": {
            "type": "string",
            "pattern": "^[a-z0-9_]{1,32}$",
            "description": "Wallet builder code"
          }
        },
        "additionalProperties": false
      }
    },
    "eip2612GasSponsoring": {},
    "erc20ApprovalGasSponsoring": {}
  },
  "x402Version": 2,
  "kairostamp_help": {
    "docs": "https://kairostamp.com/docs",
    "terms": {
      "path": "/api/v1/digest",
      "asset": "0x036CbD53842c5426634e7929541eC2318f3dCF7e",
      "price": "$0.01",
      "method": "GET",
      "pay_to": "0xdB6F694aE695C632C82677a50593B46137808453",
      "network": "eip155:84532",
      "testnet": true,
      "resource": "https://kairostamp.com/api/v1/digest",
      "amount_atomic": 10000,
      "network_label": "base-sepolia",
      "max_timeout_seconds": 300
    },
    "reason": "no_payment_offered",
    "scheme": "exact",
    "example": "curl -sS \"https://kairostamp.com/api/v1/digest?url=https://example.com\" -H \"PAYMENT-SIGNATURE: <base64 x402 exact payload>\"",
    "summary": "This endpoint is machine-payable. Pay the exact terms below, or take the free trial call first.",
    "version": 2,
    "protocol": "x402",
    "discovery": {
      "mcp": "https://kairostamp.com/mcp",
      "openapi": "https://kairostamp.com/openapi.json",
      "llms_txt": "https://kairostamp.com/llms.txt",
      "agent_card": "https://kairostamp.com/.well-known/agent-card.json"
    },
    "free_trial": {
      "note": "Send the returned token in the X-Kairostamp-Trial header on any GET /api/v1/* endpoint.",
      "claim": "curl -sS -X POST https://kairostamp.com/api/public/trial -H \"Content-Type: application/json\" -d '{\"wallet\":\"0xYourWallet\"}'",
      "description": "One free call per wallet address, forever. No payment required.",
      "spend_header": "X-Kairostamp-Trial"
    },
    "how_to_pay": [
      "Read the PAYMENT-REQUIRED header (base64 JSON) or the \"accepts\" array in this body.",
      "Sign an EIP-3009 \"exact\" authorization for $0.01 0x036CbD53842c5426634e7929541eC2318f3dCF7e on base-sepolia (eip155:84532) to 0xdB6F694aE695C632C82677a50593B46137808453.",
      "Base64-encode the x402 v2 payment payload and resend the same request with the PAYMENT-SIGNATURE header.",
      "The response is returned only after the payment settles; a platform or target failure is never charged."
    ],
    "payment_header": "PAYMENT-SIGNATURE",
    "common_mistakes": [
      "Wrong header name: use \"PAYMENT-SIGNATURE\" (x402 v2). Legacy \"X-PAYMENT\" is accepted only for compatibility.",
      "Header value must be base64 of the JSON payment payload — not raw JSON, not 0x-hex, not a bare signature.",
      "The signed amount must equal the advertised atomic amount exactly; over- and under-payment are both rejected.",
      "The signed network must match the advertised network id exactly (CAIP-2 form, e.g. eip155:8453).",
      "payTo must be the advertised address; a payment to any other address is not credited.",
      "Authorizations expire: re-sign if more than 300 seconds have passed since validAfter.",
      "Send the payment on the same request as the parameters — a bare payment with no ?url= is rejected before settlement."
    ]
  }
}

Accepts

The payment requirements as published to the catalog. Read the live 402 before paying — a price here is a claim, not a quote.

0.002USDC≈ $0.002 USD
on Base · exact scheme

Pay 0.002 USDC on Base to 0xdB6F…08453. The signed payment is good for 5 minutes.

Paid to
0xdB6F…08453
USD Coin contract
0x8335…02913
Payment window
5 minutes
As published
2000 smallest units
The catalog’s raw entry
[
  {
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "extra": {
      "name": "USD Coin",
      "version": "2"
    },
    "payTo": "0xdB6F694aE695C632C82677a50593B46137808453",
    "amount": "2000",
    "scheme": "exact",
    "network": "eip155:8453",
    "maxTimeoutSeconds": 300
  }
]

Extensions

{
  "bazaar": {
    "info": {
      "input": {
        "type": "http",
        "method": "GET",
        "queryParams": {
          "url": "https://example.com/"
        }
      },
      "output": {
        "type": "json",
        "example": {
          "receipt": {
            "url": "https://example.com/",
            "sha256": "ff67a9d764d6a2367a187734e697f6a53217db9a21c101d410a113ca871a299d",
            "fetched_at": "2026-08-23T05:32:12.771Z",
            "byte_length": 559,
            "status_code": 200,
            "content_type": "text/html",
            "text_preview": "<!doctype html><html lang=\"en\"><head><title>Example Domain</title>…",
            "redirect_chain": []
          },
          "chain_hash": "d084fff3e5d852089814f7d4d3ffe9d04d1a39ce9d2e0573a95f24cf78fb584d",
          "receipt_id": "85cd424c-b68b-440e-8f4f-e02147799f30",
          "previous_chain_hash": "da27fe24efc04330962d1b95c7929a9de901ad0ea49a7997edf9f2731bf88def"
        }
      }
    },
    "schema": {
      "type": "object",
      "$schema": "https://json-schema.org/draft/2020-12/schema",
      "required": [
        "input"
      ],
      "properties": {
        "input": {
          "type": "object",
          "required": [
            "type",
            "method"
          ],
          "properties": {
            "type": {
              "type": "string",
              "const": "http"
            },
            "method": {
              "enum": [
                "GET"
              ],
              "type": "string"
            },
            "queryParams": {
              "type": "object",
              "examples": [
                {
                  "url": "https://example.com/"
                }
              ],
              "required": [
                "url"
              ],
              "properties": {
                "url": {
                  "type": "string",
                  "format": "uri",
                  "examples": [
                    "https://example.com/"
                  ],
                  "maxLength": 2048,
                  "description": "Public http/https URL to fetch. Sent as the `url` query parameter."
                }
              },
              "additionalProperties": false
            }
          },
          "additionalProperties": false
        },
        "output": {
          "type": "object",
          "required": [
            "type"
          ],
          "properties": {
            "type": {
              "type": "string"
            },
            "example": {
              "type": "object",
              "required": [
                "receipt_id",
                "chain_hash",
                "receipt"
              ],
              "properties": {
                "receipt": {
                  "type": "object",
                  "required": [
                    "url",
                    "fetched_at",
                    "status_code",
                    "content_type",
                    "byte_length",
                    "sha256",
                    "redirect_chain"
                  ],
                  "properties": {
                    "url": {
                      "type": "string",
                      "format": "uri",
                      "description": "Final URL that was fetched."
                    },
                    "sha256": {
                      "type": "string",
                      "description": "SHA-256 of the response body bytes."
                    },
                    "fetched_at": {
                      "type": "string",
                      "format": "date-time"
                    },
                    "byte_length": {
                      "type": "integer"
                    },
                    "status_code": {
                      "type": "integer"
                    },
                    "content_type": {
                      "type": [
                        "string",
                        "null"
                      ]
                    },
                    "text_preview": {
                      "type": [
                        "string",
                        "null"
                      ]
                    },
                    "redirect_chain": {
                      "type": "array",
                      "items": {
                        "type": "string",
                        "format": "uri"
                      }
                    }
                  }
                },
                "chain_hash": {
                  "type": "string",
                  "description": "SHA-256 hash-chain value of this receipt."
                },
                "receipt_id": {
                  "type": "string",
                  "format": "uuid",
                  "description": "Evidence receipt identifier."
                },
                "previous_chain_hash": {
                  "type": [
                    "string",
                    "null"
                  ],
                  "description": "SHA-256 hash-chain value of the previous receipt."
                }
              }
            }
          }
        }
      }
    }
  },
  "builder-code": {
    "info": {
      "s": [
        "cdp_sdk_server"
      ]
    },
    "schema": {
      "type": "object",
      "$schema": "https://json-schema.org/draft/2020-12/schema",
      "properties": {
        "a": {
          "type": "string",
          "pattern": "^[a-z0-9_]{1,32}$",
          "description": "App builder code"
        },
        "s": {
          "type": "array",
          "items": {
            "type": "string",
            "pattern": "^[a-z0-9_]{1,32}$"
          },
          "maxItems": 11,
          "description": "Service builder codes"
        },
        "w": {
          "type": "string",
          "pattern": "^[a-z0-9_]{1,32}$",
          "description": "Wallet builder code"
        }
      },
      "additionalProperties": false
    }
  },
  "eip2612GasSponsoring": {},
  "erc20ApprovalGasSponsoring": {}
}

Provenance

Seen in the source catalog
2026-08-23 09:07Z
Last indexed by Roundhouse
2026-09-22 08:40Z
Last enriched (probe, favicon, geo)
2026-09-24 11:15Z
x402 version
2
Max timeout
300s
Liveness probe
HTTP 402
Report

Hand this page to an agent

Copy the prompt and paste it into Claude, an MCP client or your own agent — it will vet this service and call it over the free read API. No key, no account.

GET api.roundhouseai.io/v0/endpoints

This endpoint's own trailing-30-day call count, as published by the upstream catalog and snapshotted daily. 30 snapshots so far. Verified volume counts only settlements with an on-chain EIP-3009 marker.

Open skill.md
Show the prompt
Using Roundhouse, look up the x402 service kairostamp.com and tell me whether it is
worth paying: what a call costs, whether the endpoint answered when last probed, and what
its payment record actually shows.

curl -s 'https://api.roundhouseai.io/v0/endpoints?q=kairostamp.com'
curl -s 'https://api.roundhouseai.io/v0/merchants/<the payTo wallet returned above>'

Then call it: read the price from the live 402 at https://kairostamp.com/api/v1/digest, never from
a cached figure, and pay with an x402 client.

The /v0 API needs an API key (`authorization: Bearer rh_live_…`) on everything except
/v0/unified* and /v0/endpoints. Mint a personal key for $0.01 at GET https://api.roundhouseai.io/v0/test/x402,
or use an organization key from https://roundhouseai.io/dashboard/team.

If you do not have Roundhouse tools or skills installed, read
https://roundhouseai.io/skill.md first — it is the whole procedure.