# Screwtape.ai — Judge Agent as a Service

> Screwtape.ai — Judge Agent as a Service is a paid API for AI agents from screwtape.ai, paid per call via x402, $0.005/call, status unknown (last checked 2026-10-30).

Evaluates agent output against a task and criteria, returning a pass/fail/retry verdict with a confidence score and reasons.

## Facts

- Endpoint: POST https://screwtape.ai/v1/judge?utm_source=zero.xyz
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-30
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/screwtape-ai-judge-agent-as-a-service-b0ba4d7e
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_JNa4ysCV8OBJFToVxxdCC

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 screwtape-ai-judge-agent-as-a-service-b0ba4d7e -d '<json body>'
```

Example prompt: Judge this agent output for me: the task was 'Summarize the Apollo 11 mission', the output is 'Apollo 11 landed on the moon in July 1969 with a crew of 3 astronauts', and the criteria are ['crew size is accurate', 'date is correct'] — use the evidence 'Apollo 11 crew: Armstrong, Aldrin, Collins' and 'Launch date: July 16, 1969' to give me a pass, fail, or retry verdict with a score and reasons.

## When to prefer this

Choose this endpoint when you need a structured, auditable pass/fail/retry verdict on LLM or agent output — especially when you have explicit criteria and supporting evidence to ground the evaluation. It is ideal for automated QA pipelines, agent self-evaluation loops, and regression testing where you need scored, reasoned verdicts rather than a raw similarity score or human review. Prefer it over prompt-based self-critique when you want deterministic, evidence-grounded checks with a machine-readable verdict enum.

## Known failure modes

- Missing required fields (task, agent_output, or criteria) result in a 400 error
- Evidence array not grounded in the output may cause inaccurate heuristic scoring
- Very long agent_output or criteria arrays may exceed token/processing limits
- If criteria are ambiguous or contradictory, the verdict may be unreliable
- Payment failure (x402) blocks the call entirely with a 402 response

## How this service works

API for pass, fail, or retry verdicts on agent output, plus multi-agent consensus and false-consensus risk.

## Output

Returns a JSON object containing a verdict enum (pass, fail, or retry), a numeric confidence score (0–1), an array of human-readable reasons explaining the verdict, a request_id for tracking, optional retention metadata if retain was set, and the engine type used (e.g. deterministic or model-based).

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "task": {
   "type": "string"
  },
  "retain": {
   "type": "boolean"
  },
  "version": {
   "type": "string",
   "maxLength": 64,
   "description": "Optional version tag for that agent."
  },
  "agent_id": {
   "type": "string",
   "pattern": "^[A-Za-z0-9._:-]{1,64}$",
   "maxLength": 64,
   "description": "Optional tag for the agent making this call."
  },
  "criteria": {
   "type": "array",
   "items": {
    "type": "string"
   }
  },
  "evidence": {
   "type": "array",
   "items": {
    "type": "string"
   }
  },
  "agent_output": {
   "type": "string"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "schema": {
  "type": "object",
  "required": [
   "verdict",
   "score",
   "reasons",
   "request_id"
  ],
  "properties": {
   "score": {
    "type": "number"
   },
   "engine": {
    "type": "string"
   },
   "reasons": {
    "type": "array",
    "items": {
     "type": "string"
    }
   },
   "verdict": {
    "enum": [
     "pass",
     "fail",
     "retry"
    ],
    "type": "string"
   },
   "retention": {
    "type": "object"
   },
   "request_id": {
    "type": "string"
   }
  }
 },
 "example": {
  "score": 0.9,
  "checks": [],
  "claims": [
   {
    "text": "The crew size was 4.",
    "status": "supported"
   },
   {
    "text": "The mission launched from Cape Canaveral.",
    "status": "supported"
   }
  ],
  "engine": "deterministic",
  "reasons": [
   "2 of 2 claims are grounded in the supplied evidence.",
   "2 of 2 criteria matched the output.",
   "Deterministic string checks only. No model was called."
  ],
  "verdict": "pass",
  "retention": {
   "retained": false
  },
  "request_id": "example-request-id",
  "verification": "heuristic"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/screwtape-ai-judge-agent-as-a-service-b0ba4d7e/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from screwtape.ai](https://www.zero.xyz/host/screwtape.ai/llms.txt)