Find out why an Animica transaction would be rejected BEFORE you broadcast it

[
  {
    "scheme": "exact",
    "network": "eip155:8453",
    "payTo": "0x5D17c40FD6b119dc6006C4Ab3C20a917FCaB2aCD",
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "amount": "6000",
    "maxTimeoutSeconds": 60
  },
  {
    "scheme": "exact",
    "network": "animica:1",
    "payTo": "anim1zqpsmegc0qcvzjfukm89xs0zeu3eqyyyel7kelehuszvwfarqypky2gr946ga",
    "asset": "ANM",
    "amount": "71519389701",
    "maxTimeoutSeconds": 60
  }
]

{
  "animica": {
    "catalog": "https://animica.dev/.well-known/x402",
    "content_type": "application/json",
    "currency": "USDC",
    "description": "Find out why an Animica transaction would be rejected BEFORE you broadcast it. Decodes your canonical CBOR {body, sigs} envelope, returns the normalised fields and the CANONICAL HASH you are about to sign, then asks the node whether it would admit the transaction and why not. Both calls are read-only: nothing is inserted into the mempool and nothing is broadcast. Built for people writing Animica signers, where the alternative feedback loop is broadcast-and-see. No model.",
    "documentation": "https://animica.dev/x402#product-tx_preflight",
    "name": "Animica transaction preflight — decode and admission dry-run",
    "openapi": "https://animica.dev/x402/openapi.json",
    "price": "0.006000",
    "product": "tx_preflight",
    "provider": "Animica",
    "terms": {
      "amount_atomic": "6000",
      "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
      "chain_id": 8453,
      "network": "eip155:8453",
      "pay_to": "0x5D17c40FD6b119dc6006C4Ab3C20a917FCaB2aCD",
      "scheme": "exact"
    },
    "x402_version": 2
  },
  "bazaar": {
    "discoverable": true,
    "info": {
      "input": {
        "body": {
          "raw_tx": "0xa264626f6479a761760163676173a2656c696d69741952086570726963651a001bf5386466726f6d784030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030656e6f6e63650067636861696e496401677061796c6f6164a26174006176a362746f78403131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313131313164646174616066616d6f756e74016a6163636573734c69737480647369677380"
        },
        "bodyType": "json",
        "method": "POST",
        "type": "http"
      },
      "output": {
        "type": "json"
      }
    },
    "schema": {
      "$schema": "https://json-schema.org/draft/2020-12/schema",
      "properties": {
        "input": {
          "properties": {
            "body": {
              "properties": {
                "raw_tx": {
                  "description": "the transaction as hex, 0x-prefixed or not. Animica expects canonical CBOR of {body, sigs} with strictly-increasing map keys — non-canonical key order is the most common first failure and the decoder names it explicitly.",
                  "type": "string"
                },
                "skip_admission": {
                  "description": "decode only, skipping the admission dry-run (default false). Useful when you are iterating on encoding and do not yet have signatures attached.",
                  "type": "boolean"
                }
              },
              "required": [
                "raw_tx"
              ],
              "type": "object"
            },
            "bodyType": {
              "enum": [
                "json"
              ],
              "type": "string"
            },
            "method": {
              "enum": [
                "POST"
              ],
              "type": "string"
            },
            "queryParams": {
              "properties": {
                "raw_tx": {
                  "description": "same as body.raw_tx for GET callers",
                  "type": "string"
                },
                "skip_admission": {
                  "description": "same as body.skip_admission (\"1\"/\"true\")",
                  "type": "string"
                }
              },
              "type": "object"
            },
            "type": {
              "const": "http",
              "type": "string"
            }
          },
          "required": [
            "type",
            "method"
          ],
          "type": "object"
        },
        "output": {
          "properties": {
            "example": {},
            "type": {
              "type": "string"
            }
          },
          "required": [
            "type"
          ],
          "type": "object"
        }
      },
      "required": [
        "input"
      ],
      "type": "object"
    }
  },
  "discovery": {
    "discoverable": true,
    "info": {
      "input": {
        "bodyFields": {
          "raw_tx": {
            "description": "the transaction as hex, 0x-prefixed or not. Animica expects canonical CBOR of {body, sigs} with strictly-increasing map keys — non-canonical key order is the most common first failure and the decoder names it explicitly.",
            "required": true,
            "type": "string"
          },
          "skip_admission": {
            "description": "decode only, skipping the admission dry-run (default false). Useful when you are iterating on encoding and do not yet have signatures attached.",
            "required": false,
            "type": "boolean"
          }
        },
        "bodyType": "json",
        "method": "POST",
        "queryParams": {
          "raw_tx": {
            "description": "same as body.raw_tx for GET callers",
            "type": "string"
          },
          "skip_admission": {
            "description": "same as body.skip_admission (\"1\"/\"true\")",
            "type": "string"
          }
        },
        "type": "http"
      },
      "output": {
        "description": "as_of {read_at}; input {bytes, hex_chars}; decode {ok, canonical_hash, type, decoded_length, transaction, error {message, code, kind, cause, hint}}; admission {checked, allowed, txid, wtxid, reject_reason, error, note}; next_step; what_we_have_observed; broadcast {performed:false, how_to}; inference {used:false}.",
        "type": "json"
      }
    }
  }
}

curl "https://animica.dev/x402/tx/preflight"
# -> 402 Payment Required, accepts[] lists how to pay
# retry with a PAYMENT-SIGNATURE (or PAYMENT header) once paid

const res = await fetch("https://animica.dev/x402/tx/preflight");
if (res.status === 402) {
  const { accepts } = await res.json();
  // pay one of accepts[] via an x402 client, then retry with the payment header
}

import httpx
res = httpx.get("https://animica.dev/x402/tx/preflight")
if res.status_code == 402:
    accepts = res.json()["accepts"]
    # pay one of accepts[] via an x402 client, then retry with the payment header