# DDG Discovery Diff — Agent-Payable Well-Known Surface Auditor

> DDG Discovery Diff — Agent-Payable Well-Known Surface Auditor is a paid API for AI agents from agents.daedalusdevelopmentgroup.com, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-20).

Fetches all well-known discovery surfaces (A2A, ACP, UCP, AP2, x402), extracts claimed endpoint URLs and capabilities, probes each one at runtime (verifying payment endpoints return 402 not 200), and returns a signed per-surface claim-vs-runtime mismatch report.

## Facts

- Endpoint: POST https://agents.daedalusdevelopmentgroup.com/v1/commerce/discovery-diff?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-20
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/ddg-discovery-diff-agent-payable-well-known-surface-auditor-21fa839a
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_wk7JWFEzeEGLnbj4laF6S

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 ddg-discovery-diff-agent-payable-well-known-surface-auditor-21fa839a -d '<json body>'
```

Example prompt: Audit the discovery surfaces for my agent service at https://myservice.example.com — fetch every well-known surface (A2A, ACP, UCP, AP2, x402), probe each claimed endpoint live, and give me a signed report of any mismatches, especially whether payment endpoints are actually returning 402.

## When to prefer this

Use this endpoint when you need to verify that an agent service's self-described capabilities match its live runtime behavior, particularly in agentic commerce contexts where payment endpoints must correctly implement x402 (HTTP 402). Prefer this over manual inspection or simple HTTP checks when you need a signed, structured verdict across multiple discovery protocol surfaces simultaneously.

## Known failure modes

- Target service is unreachable — probe times out or returns connection errors for all surfaces
- Discovery surfaces return malformed or non-standard documents that cannot be parsed
- Payment endpoints return 200 instead of 402, flagged as a misconfiguration
- Target URL is missing or malformed in the request body
- Service blocks automated probes, returning 403 or rate-limit responses
- Partial surface availability — some well-known surfaces found but others missing

## How this service works

A2A/ACP/UCP/AP2/x402 discovery cross-check: fetch every well-known surface, extract the claimed endpoint URLs + capabilities, PROBE each claimed endpoint (payment endpoints must answer 402, not 200), and report per-surface claim-vs-runtime mismatches with a signed verdict. $0.01.

## Output

A signed, per-surface audit report listing each well-known discovery surface (A2A, ACP, UCP, AP2, x402) with the claimed vs observed endpoint URLs and capabilities, specific probe results for each claimed endpoint (including whether payment endpoints correctly return HTTP 402), and a final verdict indicating claim-vs-runtime mismatches or confirmation of consistency.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input",
  "output"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method",
    "bodyType",
    "body"
   ],
   "properties": {
    "body": {
     "type": "object"
    },
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "POST",
      "PUT",
      "PATCH"
     ],
     "type": "string"
    },
    "bodyType": {
     "enum": [
      "json",
      "form-data",
      "text"
     ],
     "type": "string"
    }
   },
   "additionalProperties": true
  },
  "output": {
   "type": "object",
   "required": [
    "type",
    "example"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "ok": true
    }
   },
   "additionalProperties": true
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "ok": true
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/ddg-discovery-diff-agent-payable-well-known-surface-auditor-21fa839a/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agents.daedalusdevelopmentgroup.com](https://www.zero.xyz/host/agents.daedalusdevelopmentgroup.com/llms.txt)