# FAHCE Claim Verification and Repair

> FAHCE Claim Verification and Repair is a paid API for AI agents from fahce.kinganlogic.com, paid per call via x402, $0.15/call, status unknown (last checked 2026-10-15).

Checks a candidate output against provided evidence, diagnoses contradictions, and returns a bounded step-by-step repair plan

## Facts

- Endpoint: POST https://fahce.kinganlogic.com/api/v1/verify?utm_source=zero.xyz
- Price: $0.15/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/fahce-claim-verification-and-repair-25a89b4b
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_erXK-ME6Y-RroqdI1Xv__

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 fahce-claim-verification-and-repair-25a89b4b -d '<json body>'
```

Example prompt: Can you check this draft answer against these three source documents I've uploaded and tell me which claims are unsupported or contradicted — and give me a step-by-step plan to fix them?

## When to prefer this

Choose FAHCE when you need evidence-grounded verification with an actionable, bounded repair plan rather than a simple similarity score or binary pass/fail. It is especially valuable when your pipeline produces LLM-generated text that must be audited against specific source documents before delivery, or when downstream consumers require a traceable correction audit trail. Prefer it over generic LLM self-critique loops because it grounds diagnosis in caller-supplied evidence, returns a structured machine-readable response, and provides a billing receipt suitable for automated cost accounting.

## Known failure modes

- Missing required fields (schema, evidence, or candidate_output) returns a 4xx validation error
- Evidence array is empty or too sparse to ground any claims — diagnosis may return low-confidence or indeterminate result
- candidate_output is extremely long and may hit token or processing limits
- Payment not received or x402 flow incomplete — request rejected before processing
- Contradictory evidence supplied by caller yields ambiguous repair plan
- Idempotency key collision returns cached prior result rather than re-processing

## How this service works

Review claims against evidence, resolve contradictions, and get a bounded repair plan with FAHCE.

## Output

A structured FAHCE_MACHINE_RESPONSE_V1 object containing: a diagnosis of which claims pass or fail against evidence, a repair plan with bounded numbered steps and authority notes, a proposed corrected output string, billing determination (billable/free-retry), a cryptographic receipt, and a recommended next safe action for the calling agent.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "schema",
  "evidence",
  "candidate_output"
 ],
 "properties": {
  "schema": {
   "type": "string"
  },
  "evidence": {
   "type": "array"
  },
  "expected_output": {
   "type": "string",
   "description": "Optional response-contract and repair-target context for all operations, including Diagnose. Supported response-format directives (for example, Return JSON) and implemented explicit constraints can affect the diagnosis. Ordinary matching or mismatching factual text is not compared for string equality and is not a trusted answer oracle or supporting evidence; supply independent evidence for factual claims."
  },
  "candidate_output": {
   "type": "string",
   "description": "The exact candidate output to diagnose or verify. Never use payment evidence as semantic evidence."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "schema",
  "operation",
  "request_id",
  "input_hash",
  "diagnosis",
  "repair",
  "verification",
  "billing",
  "receipt",
  "next_safe_action"
 ],
 "properties": {
  "repair": {
   "anyOf": [
    {
     "type": "object",
     "required": [
      "plan",
      "treatment",
      "proposed_output",
      "status"
     ],
     "properties": {
      "plan": {
       "type": "object",
       "required": [
        "required",
        "bounded_steps",
        "authority_note"
       ],
       "properties": {
        "required": {
         "type": "boolean"
        },
        "validated_ir": {
         "type": "object"
        },
        "bounded_steps": {
         "type": "array",
         "items": {
          "type": "object",
          "required": [
           "step",
           "boundary"
          ],
          "properties": {
           "step": {
            "type": "string"
           },
           "boundary": {
            "type": "string"
           }
          },
          "additionalProperties": false
         }
        },
        "authority_note": {
         "type": "string"
        },
        "claim_corrections": {
         "type": "array",
         "items": {
          "type": "object"
         }
        }
       }
      },
      "status": {
       "const": "PROPOSED_NOT_EXECUTED"
      },
      "treatment": {
       "type": [
        "object",
        "null"
       ]
      },
      "proposed_output": {
       "type": [
        "string",
        "null"
       ]
      }
     },
     "additionalProperties": false
    },
    {
     "type": "null"
    }
   ]
  },
  "schema": {
   "const": "FAHCE_MACHINE_RESPONSE_V1"
  },
  "billing": {
   "type": "object",
   "required": [
    "billable",
    "free_retry",
    "reason",
    "determination_status"
   ],
   "properties": {
    "reason": {
     "type": [
      "string",
      "null"
     ]
    },
    "billable": {
     "type": "boolean"
    },
    "free_retry": {
     "type": "boolean"
    },
    "determination_status": {
     "enum": [
      "DETERMINATION_COMPLETE",
      "DETERMINATION_COMPLETE_NEGATIVE",
      "DETERMINATION_NOT_PRODUCED"
     ]
    }
   }
  },
  "binding": {
   "type": "object",
   "required": [
    "actor_id",
    "tenant_id",
    "nonce",
    "idempotency_key"
   ],
   "properties": {
    "nonce": {
     "type": "string"
    },
    "actor_id": {
     "type": "string"
    },
    "tenant_id": {
     "type": "string"
    },
    "tenant_model": 
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/fahce-claim-verification-and-repair-25a89b4b/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from fahce.kinganlogic.com](https://www.zero.xyz/host/fahce.kinganlogic.com/llms.txt)