Struct X402Challenge 

pub struct X402Challenge {
    pub scheme: String,
    pub asset: String,
    pub network: Option<String>,
    pub amount_atomic: u128,
    pub decimals: u32,
    pub pay_to: Option<String>,
    pub resource: Option<String>,
}

A parsed x402 402 Payment Required challenge — the price quote an agent must clear before a paywalled call succeeds.

Built from the JSON an x402 server returns ({ "x402Version", "accepts": [ requirements… ], "error"? }) via X402Challenge::from_body, or from a single requirements object via X402Challenge::from_requirements. Field names track the x402 PaymentRequirements shape; the amount is kept in the asset’s smallest (atomic) unit, exactly as quoted, so no precision is lost before normalization.

Fields

scheme: String

Payment scheme, e.g. "exact" (the canonical x402 scheme).

asset: String

Settlement asset symbol, e.g. "USDC".

network: Option<String>

Settlement network, e.g. "base-sepolia". Optional — informational.

amount_atomic: u128

Quoted amount in the asset’s atomic unit (e.g. 6-decimal USDC: 10_000 == $0.01). Kept exact; normalization to cents happens in X402Challenge::to_cost_event.

decimals: u32

Asset decimals used to interpret amount_atomic (USDC/USDT/PYUSD = 6, DAI = 18).

pay_to: Option<String>

Destination address the payment would settle to. Optional; recorded, not validated.

resource: Option<String>

The paywalled resource URL the 402 guards. Optional.

Implementations

impl X402Challenge

pub fn from_body(body: &Value) -> Option<Self>

Parse the full body of an x402 402 response ({ "x402Version", "accepts": [ … ], "error"? }), taking the first entry of accepts (x402 lists a server’s acceptable payment options most-preferred-first). Returns None if the body has no usable requirements object.

pub fn from_requirements(req: &Value) -> Option<Self>

Parse a single x402 PaymentRequirements object.

Reads scheme (default "exact"), network, payTo, resource, the atomic amount (maxAmountRequired | amount, string or number), and the asset symbol + decimals (from extra.name/extra.decimals, or the top-level asset/symbol/decimals). Missing decimals are inferred from the known-stablecoin table. Returns None when no amount can be read — an unquoted challenge is not a price.

pub fn to_cost_event(&self) -> Option<X402CostEvent>

Normalize the quoted price to a X402CostEvent in cents — the common budget unit.

Only assets with a known 1:1 USD peg (the stablecoins in [is_usd_pegged]) can be priced offline. For those, cents = ⌈amount_atomic · 100 / 10^decimals⌉: integer math, rounded up, so a sub-cent quote is never charged as free (which would let a stream of dust payments slip the budget). Any other asset returns None — see the module’s deny-by-default note.

pub fn summary(&self) -> String

A short human-readable summary of the quote, for alerts + audit reasons.

Trait Implementations

impl Clone for X402Challenge

fn clone(&self) -> X402Challenge

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for X402Challenge

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for X402Challenge

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Eq for X402Challenge

impl PartialEq for X402Challenge

fn eq(&self, other: &X402Challenge) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl Serialize for X402Challenge

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for X402Challenge