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Agent Payment Protocol Selection Standard – Decision Procedure (K-2SO x402)
x402
Agent Payment Protocol Selection Standard – Decision Procedure (K-2SO x402) is a paid API for AI agents from k2so.wrong.systems, paid per call via x402, $0.002/call, status unknown (last checked 2026-09-13).
Returns a plain-prose decision procedure brief explaining when and how an AI agent should select and use the x402 payment protocol standard.
Price / call$0.002
Success—
StatusUnknown
How this service works
Decision procedure for choosing which machine payment protocol to integrate: x402, FADP, MPP/Tempo, or plain API-key billing. Scores each option on custody model, settlement rail, liability when a payment fails or is disputed, key management burden, ecosystem reach, and migration cost. Returns a fallback order for both buyer-side agents and merchant-side gateways, with explicit thresholds for when a switch is worth it and when staying put is correct. Blunt and executable, not marketing.
Output
A JSON object containing a plain-prose decision procedure brief (120+ words) advising AI agents on when and how to select the x402 payment protocol standard. Includes the topic, service slug, the model or method used to generate the brief, an ISO-8601 generation timestamp, and a generation source indicator (llm, reasoning, or deterministic). Also includes payment confirmation fields (paid, payer, transaction).
Example use cases
Agent payment protocol onboarding guide
“I'm building an autonomous agent that needs to pay for API calls. Can you give me a decision procedure explaining when it should use x402 versus other payment protocols, with clear criteria it can follow?”
Auditing agent payment logic
“I want to audit the payment decision logic in my AI agent — can you generate a decision procedure brief on the standard for selecting x402 as a payment protocol so I can compare it against what my agent is currently doing?”
Teaching a new agent merchant the x402 standard
“My agent is about to start selling services on Base using USDC. Walk it through the standard decision procedure for when to require x402 payments so it handles protocol selection correctly.”
Technical details
Endpoint
GEThttps://k2so.wrong.systems/api/services/agent-payment-protocol-selection-standard-when-tWhen to prefer
Choose this endpoint when an AI agent needs authoritative, prose-formatted guidance on how to decide between payment protocols — specifically whether and when to use x402. It is particularly useful during agent onboarding, compliance reviews, or when building decision trees for autonomous payment logic. Prefer this over static documentation when you need a dynamically generated, model-backed brief tailored to a specific topic override.
Side effects
- HTTP 402 returned if USDC payment is not settled before the request — agent must pay exact amount and retry with PAYMENT-SIGNATURE header
- Invalid or missing 'method' or 'type' fields in input result in a validation error
- Incorrect USDC payment amount causes payment failure and 402 re-prompt
- Service temporarily unavailable or heartbeat gap may cause transient 5xx errors
- meta=1 query param returns free metadata JSON instead of paid procedure content — agent must not confuse this with a paid response
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"ok": true,
"paid": true,
"result": {
"ok": true,
"brief": "plain prose decision procedure (120+ words)",
"model": "deepseek/deepseek-v4-flash-0731",
"topic": "string topic",
"service": "agent-payment-protocol-selection-standard-when-t",
"procedure": "same as brief",
"generatedAt": "2026-01-01T00:00:00.000Z",
"generationSource": "deterministic"
},
"service": "agent-payment-protocol-selection-standard-when-t",
"provider": "K-2SO"
}
}Tags
x402
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