# X402 Quote Comparison and Selection Procedure

> X402 Quote Comparison and Selection Procedure is a paid API for AI agents from k2so-8080.on.ascii.dev, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-23).

Returns a ranked quote comparison table and winning-merchant decision procedure for agents buying a single x402 service from multiple competing merchants without accounts or OAuth

## Facts

- Endpoint: GET https://k2so-8080.on.ascii.dev/api/services/rt-nichxbt-x402-ai-agent-grocery-shopping-an-age?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-23
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-quote-comparison-and-selection-procedure-b94125db
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_FB32T8ueiFZ_S-81uvVdX

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability x402-quote-comparison-and-selection-procedure-b94125db
```

Example prompt: I need to buy a weather data feed from one of several x402 merchants — can you run the quote comparison procedure to figure out which one is the best deal including fees, check their trust tiers, and flag any with mismatched payTo or stale offers before I commit?

## When to prefer this

Use this endpoint when an agent must autonomously choose among multiple competing x402 merchants for a single service purchase without human intervention, accounts, or OAuth. It is specifically designed for the x402 payment protocol context and handles trust tier ranking, fee normalization, stale-offer detection, and fallback planning in a single call — making it superior to generic comparison logic when x402-specific kill criteria (mismatched payTo, weak HTTP contracts) matter.

## Known failure modes

- All merchants fail kill criteria (404/405, mismatched payTo, stale offers) — no winner selected
- Topic override not recognized — falls back to default procedure
- Service temporarily unavailable at the provider host
- Malformed or incomplete merchant offer data causes normalization failure
- LLM generation failure results in degraded or missing prose rationale

## How this service works

Decision procedure for an agent buying one service from multiple x402 merchants without accounts or OAuth. Collects offers, probes each for real 402 challenges, normalizes quotes to comparable units (total cost incl fees, settlement latency, data freshness), applies merchant trust tier and kill criteria (404/405 weak contracts, mismatched payTo, stale offers), then selects the winning quote with explicit rationale and records a runner-up for re-quote fallback. Returns a ranked quote table with

## Output

A ranked quote table comparing all probed x402 merchants, with normalized total cost (including fees), settlement latency, data freshness scores, merchant trust tier, kill-criteria pass/fail flags, the winning merchant with explicit rationale, and a designated runner-up for re-quote fallback. Response also includes a prose decision brief for agent consumption and generation metadata (model, timestamp, source).

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "properties": {
      "meta": {
       "enum": [
        "0",
        "1"
       ],
       "type": "string",
       "description": "Set to 1 for free metadata JSON (no payment required)"
      },
      "topic": {
       "type": "string",
       "description": "Optional topic override for the decision procedure"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "title": "agent-x402-quote-comparison-and-selection-procedure paid response",
     "$schema": "https://json-schema.org/draft/2020-12/schema",
     "required": [
      "ok",
      "paid",
      "service",
      "provider",
      "result"
     ],
     "properties": {
      "ok": {
       "type": "boolean"
      },
      "paid": {
       "type": "boolean"
      },
      "result": {
       "type": "object",
       "required": [
        "ok",
        "service"
       ],
       "properties": {
        "ok": {
         "type": "boolean",
         "description": "Handler success"
        },
        "brief": {
         "type": "string",
         "description": "Decision procedure prose for agents"
        },
        "model": {
         "type": "string"
        },
        "topic": {
         "type": "string"
        },
        "service": {
         "type": "string",
         "description": "Service slug"
        },
        "procedure": {
         "type": "string"
        },
        "generatedAt": {
         "type": "string",
         "description": "ISO-8601 timestamp"
        },
        "generationSource": {
         "enum": [
          "llm",
          "reasoning",
          "deterministic"
         ],
         "type": "string"
        }
       }
      },
      "payment": {
       "type": "object",
       "properties": {
        "code": {
         "type": "string"
        },
        "payer": {
         "type": "string"
        },
        "detail": {
         "type": "string"
  
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-quote-comparison-and-selection-procedure-b94125db/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from k2so-8080.on.ascii.dev](https://www.zero.xyz/host/k2so-8080.on.ascii.dev/llms.txt)