# Source-Backed Search

> Source-Backed Search is a paid API for AI agents from phion.systems, paid per call via x402, $0.004/call, status unknown (last checked 2026-10-20).

Search a set of user-supplied public sources and return only results that are literally attested by those sources, with no hallucinated or inferred content

## Facts

- Endpoint: POST https://phion.systems/v1/paid/trust/source-backed-search?utm_source=zero.xyz
- Price: $0.004/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-20
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/source-backed-search-3a60f742
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_XaCzYURYUSBO8_k6Gy4AO

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 source-backed-search-3a60f742 -d '<json body>'
```

Example prompt: Search these three URLs — [source1], [source2], [source3] — for anything they literally say about 'GDPR data retention requirements' and return only the exact matching text with source citations, no inferences.

## When to prefer this

Choose this endpoint when you need search results that are strictly grounded in a specific set of user-supplied public sources with zero tolerance for hallucination or inference — ideal for compliance, fact-checking, or legal evidence workflows where only literal source text is acceptable. Prefer it over general web search when you already know which sources are authoritative and need cryptographically-attested, citation-backed results rather than ranked web results.

## Known failure modes

- Source URL is inaccessible or returns non-200 — no results returned for that source
- Query finds no literal matches in any of the supplied sources — empty result set returned
- Supplied URLs are not public or require authentication — retrieval fails
- Malformed input schema — request rejected
- Rate limit or budget exceeded — 402 or budget guard rejection

## How this service works

Search supplied public sources and return only literal source-backed matches

## Output

A set of literal, source-backed matches extracted from the supplied public URLs: each result includes the matched text excerpt exactly as it appears in the source, the source URL, and attestation metadata confirming the match is grounded in the actual source content rather than inferred or generated.

## 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/source-backed-search-3a60f742/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)