API · x402

Is this transaction, approval or signature safe to sign, explained for a person

Is this transaction, approval or signature safe to sign, explained for a person? The same pre-sign verdict as /v1/check (green/orange/red + reason codes) plus a short plain-language explanation in English or Dutch, for an agent to show its user before asking…

by presign-guard.fizzl.eu · discovered, not yet claimed by its owner · updated 2026-10-08

Mirrored from Coinbase's public x402 Bazaar. The description is the provider's own text and has not been reviewed here; the payment requirements are copied as published.

What it does

Tags: wallet-security · pre-sign · approvals · sanctions · agents · bazaar

Use with an agent

Discover. Agents find this listing with GET https://bazaar.saylorinnovations.com/discovery/search?query=…, the MCP tool search_resources, or /discovery/resources.
Inspect. Fetch /resources/34929.json for the price and payment options.
Pay. Call GET https://presign-guard.fizzl.eu/v1/check/explain. The provider answers 402 with its payment requirements. An x402 client signs one of the options below and retries with PAYMENT-SIGNATURE.
Execute. The provider returns 200 with the data. Agent Bazaar is not in the request path and never sees your payment.

For humans

You don't need an account or an API key; you need a wallet holding a small amount of USDC on Base, xrpl:0, algorand:wGHE2Pwdvd7S12BL5FaOP20EGYesN73ktiC1qzkkit8=, and an x402-capable client (see the examples below). Call the endpoint unpaid first to see exactly what it asks for.

Pricing & payment

Price: $0.03 / request
Protocol: x402 v2
Auth: No account or API key. Pay per request.
Networks: Base, xrpl:0, algorand:wGHE2Pwdvd7S12BL5FaOP20EGYesN73ktiC1qzkkit8=
Calls (30d): 2 · 2 unique payers (third-party data from the public x402 Bazaar)

x402 payment requirements

Scheme	Network	Asset	Amount	Pay to	Timeout
exact	Base eip155:8453	USDC	$0.03	0x6B0F4651eD42893ab58139938175E4a69f175F25	300s
exact	xrpl:0 xrpl:0	524C555344000000000000000000000000000000	0.03	r9xmBsRr8Ao7jRgjjxreMiAwGiCK2FGwqw	300s
exact	algorand:wGHE2Pwdvd7S12BL5FaOP20EGYesN73ktiC1qzkkit8= algorand:wGHE2Pwdvd7S12BL5FaOP20EGYesN73ktiC1qzkkit8=	31566704	30000	LOYVFSQ6ZTS2YWUW4GQ5L6VPP2TPIOXWYDACK53CPOHQQHLDMEMKJDXAX4	300s

accepts[] (raw JSON)

[
  {
    "scheme": "exact",
    "network": "eip155:8453",
    "payTo": "0x6B0F4651eD42893ab58139938175E4a69f175F25",
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "amount": "30000",
    "amountUsd": 0.03,
    "maxTimeoutSeconds": 300
  },
  {
    "scheme": "exact",
    "network": "xrpl:0",
    "payTo": "r9xmBsRr8Ao7jRgjjxreMiAwGiCK2FGwqw",
    "asset": "524C555344000000000000000000000000000000",
    "amount": "0.03",
    "maxTimeoutSeconds": 300
  },
  {
    "scheme": "exact",
    "network": "algorand:wGHE2Pwdvd7S12BL5FaOP20EGYesN73ktiC1qzkkit8=",
    "payTo": "LOYVFSQ6ZTS2YWUW4GQ5L6VPP2TPIOXWYDACK53CPOHQQHLDMEMKJDXAX4",
    "asset": "31566704",
    "amount": "30000",
    "maxTimeoutSeconds": 300
  }
]

Schemas

Output schema (JSON Schema)

{
  "properties": {
    "example": {
      "properties": {
        "explanation": {
          "properties": {
            "lang": {
              "type": "string"
            },
            "text": {
              "type": "string"
            }
          },
          "type": "object"
        },
        "reasons": {
          "items": {
            "properties": {
              "code": {
                "type": "string"
              },
              "details": {},
              "severity": {
                "enum": [
                  "red",
                  "orange",
                  "info"
                ],
                "type": "string"
              },
              "subject": {
                "type": "string"
              }
            },
            "required": [
              "code",
              "severity"
            ],
            "type": "object"
          },
          "type": "array"
        },
        "receipt": {
          "description": "Signature over this whole answer (without receipt.signature), so the verdict can be verified later: EIP-191 personal_sign over canonical JSON (sorted keys, compact, ASCII-escaped). Signer addresses: /.well-known/presign-guard-signer.json; free check: POST /v1/verify.",
          "properties": {
            "algorithm": {
              "enum": [
                "eip191-canonical-json-v1"
              ],
              "type": "string"
            },
            "cert": {
              "description": "The payout wallet's certificate for this signing key: personal_sign by authority over 'fizzl receipt signer\\nservice: <service>\\nsigner: <signer>\\nvalid_from: <date>'. Pin the payout wallet and a rotated key still verifies.",
              "properties": {
                "authority": {
                  "type": "string"
                },
                "service": {
                  "type": "string"
                },
                "signature": {
                  "type": "string"
                },
                "signer": {
                  "type": "string"
                },
                "valid_from": {
                  "type": "string"
                }
              },
              "type": "object"
            },
            "input_sha256": {
              "description": "sha256 of canonical JSON {route, input}: your body (POST) or query parameters (GET)",
              "type": "string"
            },
            "payment": {
              "description": "The payment behind this answer, from your x402 payment payload. EVM: payer + EIP-3009 nonce; find the settlement as AuthorizationUsed(payer, nonce) on the asset contract. Solana: payer + sha256 of the signed transaction you sent.",
              "properties": {
                "amount": {
                  "type": "string"
                },
                "asset": {
                  "type": "string"
                },
                "network": {
                  "type": "string"
                },
                "nonce": {
                  "type": "string"
                },
                "pay_to": {
                  "type": "string"
                },
                "payer": {
                  "type": "string"
                },
                "proof": {
                  "enum": [
                    "eip3009",
                    "svm-transaction"
                  ],
                  "type": "string"
                },
                "transaction_sha256": {
                  "type": "string"
                }
              },
              "type": "object"
            },
            "request_id": {
              "type": "string"
            },
            "route": {
              "type": "string"
            },
            "signature": {
              "type": "string"
            },
            "signed_at": {
              "type": "string"
            },
            "signer": {
              "type": "string"
            }
          },
          "required": [
            "request_id",
            "route",
            "input_sha256",
            "signed_at",
            "signer",
            "algorithm",
            "signature"
          ],
          "type": "object"
        },
        "subject": {
          "type": "object"
        },
        "verdict": {
          "enum": [
            "green",
            "orange",
            "red"
          ],
          "type": "string"
        }
      },
      "required": [
        "verdict",
        "reasons"
      ],
      "type": "object"
    },
    "type": {
      "type": "string"
    }
  },
  "required": [
    "type"
  ],
  "type": "object"
}

Example shape — generated from the schema, not a captured live response

{
  "example": {
    "explanation": {
      "lang": "string",
      "text": "string"
    },
    "reasons": [
      {
        "code": "string",
        "details": null,
        "severity": "red",
        "subject": "string"
      }
    ],
    "receipt": {
      "algorithm": "eip191-canonical-json-v1",
      "cert": {
        "authority": "string",
        "service": "string",
        "signature": "string",
        "signer": "string",
        "valid_from": "string"
      },
      "input_sha256": "string",
      "payment": {
        "amount": "string",
        "asset": "string",
        "network": "string",
        "nonce": "string",
        "pay_to": "string",
        "payer": "string",
        "proof": "eip3009",
        "transaction_sha256": "string"
      },
      "request_id": "string",
      "route": "string",
      "signature": "string",
      "signed_at": "string",
      "signer": "string"
    },
    "subject": {},
    "verdict": "green"
  },
  "type": "string"
}

Examples

curl

curl "https://presign-guard.fizzl.eu/v1/check/explain"
# -> 402 Payment Required, accepts[] lists how to pay
# retry with a PAYMENT-SIGNATURE (or PAYMENT header) once paid

JavaScript

const res = await fetch("https://presign-guard.fizzl.eu/v1/check/explain");
if (res.status === 402) {
  const { accepts } = await res.json();
  // pay one of accepts[] via an x402 client, then retry with the payment header
}

Python

import httpx
res = httpx.get("https://presign-guard.fizzl.eu/v1/check/explain")
if res.status_code == 402:
    accepts = res.json()["accepts"]
    # pay one of accepts[] via an x402 client, then retry with the payment header

Details

Provider: presign-guard.fizzl.eu
Endpoint: https://presign-guard.fizzl.eu/v1/check/explain
Machine-readable: /resources/34929.json