# Capability Verification

> Capability Verification is a paid API for AI agents from phion.systems, paid per call via x402, $0.003/call, status unknown (last checked 2026-10-20).

Compares claimed agent or service capabilities against independently evidenced, observed successful outcomes to verify truthfulness

## Facts

- Endpoint: POST https://phion.systems/v1/paid/trust/capability-verification?utm_source=zero.xyz
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-20
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/capability-verification-366bc73d
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap__-OOo_KLh2vewTjlW1nxo

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 capability-verification-366bc73d -d '<json body>'
```

Example prompt: Before I let this agent handle my invoice processing, can you check whether its claimed capability to extract and categorize invoice line items is backed by independently evidenced successful observations — flag any mismatches?

## When to prefer this

Use this endpoint when you need independent, evidenced verification of capability claims rather than self-reported or unverified assertions — especially before delegating high-value tasks, onboarding third-party agents, or entering agentic commerce relationships. Prefer this over capability negotiation preflight when you specifically need evidence-backed validation of past performance rather than just a compatibility check of offered vs. required specs.

## Known failure modes

- Insufficient evidence observations provided to compare against claims
- Capability claims are too vague or ambiguous to match against evidence
- External evidence sources unavailable or unreachable at verification time
- Input schema missing required capability or evidence fields, resulting in a 400-level error
- Payment not confirmed, resulting in a 402 response requiring x402 payment flow

## How this service works

Compare claimed capabilities with independently evidenced successful observations

## Output

Returns a structured comparison of claimed versus independently evidenced capabilities, including a match/mismatch assessment, which specific claims are supported or unsubstantiated, and any discrepancies detected between stated and observed successful outcomes.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input",
  "output"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "body"
   ],
   "properties": {
    "body": {
     "type": "object",
     "additionalProperties": true
    }
   }
  },
  "output": {
   "type": "object",
   "required": [
    "example"
   ],
   "properties": {
    "example": {
     "type": "object",
     "additionalProperties": true
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json"
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/capability-verification-366bc73d/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from phion.systems](https://www.zero.xyz/host/phion.systems/llms.txt)