Verify

Validates a client's signed payment payload against the resource server's payment requirements without submitting any transaction on-chain.

Resource servers can use this endpoint to confirm a payment is valid before serving a response, while deferring the on-chain settlement to a later step via /settle.

POST /verify

Request body

Property	Type	Required	Description
paymentPayload	object	Yes	The signed payment payload submitted by the client.
paymentRequirements	object	Yes	The payment requirements declared by the resource server.

paymentPayload

Property	Type	Description
x402Version	integer	Protocol version. Must be 2.
payload	object	Casper-specific signed authorization. See below.
resource	object	Information about the resource being accessed. See below.
accepted	object	Accepted payment option. See below.

accepted

The accepted payment option:

Property	Type	Description
scheme	string	Payment scheme. Must be "exact".
network	string	CAIP-2 network identifier (e.g. "casper:casper-net-1").
asset	string	CEP-18 contract package hash as a 64-character hex string.
amount	string	Required payment amount in token base units as a decimal string.
payTo	string	Casper account hash of the intended recipient (format: 00<64 hex chars>).
maxTimeoutSeconds	integer	Maximum number of seconds the authorization must remain valid from now. Minimum 6.
extra	object	Optional token metadata (e.g. name, version) used to build the EIP-712 domain.

resource

Property	Type	Required	Description
url	string	Yes	URL of the resource being accessed.
description	string	No	Human-readable description of the resource.
mimeType	string	No	MIME type of the resource (e.g. "text/html").

The payload object contains:

Property	Type	Description
signature	string	65-byte EIP-712 signature as a hex string (130 characters).
publicKey	string	Casper public key as a hex string with an algorithm prefix (01 for ED25519, 02 for SECP256K1).
authorization	object	EIP-712 TransferAuthorization typed data. See below.

The authorization object contains:

Property	Type	Description
from	string	Casper account hash of the payer (format: 00<64 hex chars>).
to	string	Casper account hash of the payee (format: 00<64 hex chars>).
value	string	Payment amount in token base units as a decimal string.
validAfter	string	Unix timestamp (seconds) before which the authorization is not valid.
validBefore	string	Unix timestamp (seconds) after which the authorization expires.
nonce	string	32-byte random nonce as a hex string (64 characters).

paymentRequirements

An object describing the required payment. The facilitator validates the authorization against these requirements.

Property	Type	Description
scheme	string	Payment scheme. Must be "exact".
network	string	CAIP-2 network identifier. Must match the network in paymentPayload.
payTo	string	Casper account hash of the intended recipient (format: 00<64 hex chars>).
amount	string	Required payment amount in token base units as a decimal string.
asset	string	CEP-18 contract package hash as a 64-character hex string.
maxTimeoutSeconds	integer	Maximum number of seconds the authorization must remain valid from now. Minimum 6.
extra	object	Token metadata. Must include name and version to build the EIP-712 domain.

Response

Property	Type	Description
isValid	boolean	true if the payload is valid, false otherwise.
payer	string	Account hash of the payer, present when isValid is true.
invalidReason	string	Machine-readable error code, present when isValid is false.
invalidMessage	string	Human-readable error description, present when isValid is false.
extensions	object	Optional additional data returned by the facilitator.

Error codes

Code	Description
unsupported_scheme	The payment scheme is not "exact".
network_mismatch	Payload and requirements specify different networks.
malformed_payload	Missing or invalid fields, or malformed nonce/signature hex.
pay_to_mismatch	authorization.to does not match requirements.payTo.
amount_mismatch	authorization.value does not match requirements.amount.
invalid_pay_to	payTo is not a valid Casper account hash.
invalid_amount	Amount is zero or empty.
invalid_asset	Asset is not a valid 64-character hex CEP-18 package hash.
not_yet_valid	Current time is before validAfter.
payload_expired	Current time is past validBefore.
insufficient_time	Less than 6 seconds remain before validBefore.
missing_token_name / missing_token_version	Required EIP-712 domain fields are absent from extra.
failed_to_hash	Failed to compute the EIP-712 typed-data digest.
invalid_signature	Signature does not verify against the public key and EIP-712 digest.

Example

curl -X 'POST' \
  'https://x402-facilitator.cspr.cloud/verify' \
  -H 'authorization: 55f79117-fc4d-4d60-9956-65423f39a06a' \
  -H 'accept: application/json' \
  -H 'content-type: application/json' \
  -d '{
    "paymentPayload": {
      "x402Version": 2,
      "resource": {
          "url": "http://127.0.0.1:3002/api/data"
      },
      "accepted": {
          "scheme": "exact",
          "network": "casper:casper-test",
          "asset": "9824d60dc3a5c44a20b9fd260a412437933835b52fc683d8ae36e4ec2114843e",
          "amount": "10000",
          "payTo": "0000000000000000000000000000000000000000000000000000000000000000",
          "maxTimeoutSeconds": 300
      },
      "payload": {
        "signature": "01a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f601",
        "publicKey": "0176197d7191ce519ed043221956a2227921abf30364d4362970229027ec828f04",
        "authorization": {
          "from":        "00048a54220799a48171743407c086668bdcc788e2a31e4185fe52d0682634f888",
          "to":          "009e5669b070545e2b32bc66363b9d3d4390fca56bf52a05f1411b7fa18ca311c7",
          "value":       "10000",
          "validAfter":  "1710000000",
          "validBefore": "1710000900",
          "nonce":       "a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4e5f6a1b2"
        }
      }
    },
    "paymentRequirements": {
      "scheme": "exact",
      "network": "casper:casper-test",
      "payTo":  "009e5669b070545e2b32bc66363b9d3d4390fca56bf52a05f1411b7fa18ca311c7",
      "amount": "10000",
      "asset":  "9824d60dc3a5c44a20b9fd260a412437933835b52fc683d8ae36e4ec2114843e",
      "maxTimeoutSeconds": 900,
      "extra": {
        "name":     "Cep18x402",
        "version":  "1",
        "decimals": "2",
        "symbol":   "CSPR"
      }
    }
  }'

{
  "isValid": true,
  "payer": "00048a54220799a48171743407c086668bdcc788e2a31e4185fe52d0682634f888"
}

When verification fails, the response includes invalidReason and invalidMessage instead of payer:

{
  "isValid": false,
  "invalidReason": "invalid_signature",
  "invalidMessage": "Signature does not verify against the public key and EIP-712 digest."
}