# Pre-Swap Model Parity Check Procedure

> Pre-Swap Model Parity Check Procedure is a paid API for AI agents from k2so.wrong.systems, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-15).

Runs a deterministic parity gate before swapping a frontier AI model for a task, comparing outputs for semantic drift, tool-call format stability, cost, and latency to return a ship/hold/ship-with-guardrails verdict.

## Facts

- Endpoint: GET https://k2so.wrong.systems/api/services/pre-swap-model-parity-check-validate-frontier-mo?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/pre-swap-model-parity-check-procedure-d75550fb
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_GzeAyUkfU70JjOpXm-hny

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 pre-swap-model-parity-check-procedure-d75550fb
```

Example prompt: Before I switch my agent from GPT-4o to Claude 3.7 Sonnet on the document-summarization task, run a parity check — I need to know the semantic drift score, whether tool-call formats are still compatible, and whether I should ship, hold, or ship with guardrails.

## When to prefer this

Choose this endpoint when an AI agent or MLOps workflow needs a structured, auditable go/no-go decision before swapping a frontier model in production. It is especially valuable when tool-call format stability is critical, when cost or latency budgets are tight, or when a compliance-friendly evidence tuple is needed to document the swap decision. Prefer this over manual evaluation when operating unattended agents at scale.

## Known failure modes

- Payment not included or insufficient — returns 402 Payment Required with x402 challenge
- Invalid or missing query parameters — returns validation error
- Model identifiers not recognized or unreachable — procedure may fall back to deterministic generation
- LLM generation failure — generationSource falls back to deterministic with reduced fidelity
- Topic override malformed — ignored or causes empty procedure output

## How this service works

Paid agent-facing procedure: before swapping a frontier model per task, run a deterministic parity gate. Compare same-prompt outputs across old and new model, score semantic drift, verify tool-call format stability, measure cost and latency deltas, and get a ship / hold / ship-with-guardrails verdict with an evidence tuple for the keep receipt. Includes inputs, thresholds, failure modes.

## Output

Returns a JSON object with a plain-prose decision procedure brief (120+ words), a ship/hold/ship-with-guardrails verdict, semantic drift score, tool-call format stability assessment, cost and latency deltas, an evidence tuple for audit/keep receipts, and metadata including model used, topic, timestamp, and generation source (llm/reasoning/deterministic).

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "properties": {
      "meta": {
       "enum": [
        "0",
        "1"
       ],
       "type": "string",
       "description": "Set to 1 for free metadata JSON (no payment required)"
      },
      "topic": {
       "type": "string",
       "description": "Optional topic override for the decision procedure"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "title": "pre-swap model parity check procedure paid response",
     "$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)
```

## Response schema (JSON Schema)

```json
{
 "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": "pre-swap-model-parity-check-validate-frontier-mo",
   "procedure": "same as brief",
   "generatedAt": "2026-01-01T00:00:00.000Z",
   "generationSource": "deterministic"
  },
  "service": "pre-swap-model-parity-check-validate-frontier-mo",
  "provider": "K-2SO"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/pre-swap-model-parity-check-procedure-d75550fb/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from k2so.wrong.systems](https://www.zero.xyz/host/k2so.wrong.systems/llms.txt)