# Toll402 Trusted-Source Lookup & Synthesis

> Toll402 Trusted-Source Lookup & Synthesis is a paid API for AI agents from toll402.dev, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-15).

Retrieves cited passages from trusted sources (Wikipedia, Wikidata, arXiv, Crossref, World Bank) for a query, optionally synthesizing an LLM answer that cites those passages.

## Facts

- Endpoint: GET https://toll402.dev/v1/lookup
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/toll402-trusted-source-lookup-synthesis-c830f40c
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_TqWFa0VfzQUy-MGOXKzkT

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 toll402-trusted-source-lookup-synthesis-c830f40c
```

Example prompt: Search Wikipedia, arXiv, and Crossref for reliable cited passages about the long-term health effects of intermittent fasting, then synthesize an answer that cites those passages and admits what the sources don't cover.

## When to prefer this

Choose this endpoint when you need factual answers grounded in identifiable, citable sources with reliability tiers — especially for academic, encyclopedic, or economic questions where provenance and citation matter. Prefer it over general web search when you need traceable references (DOIs, Wikidata IDs, Wikipedia URLs) rather than raw web results. It is particularly strong for research assistance, fact-checking pipelines, and citation generation where the agent must admit uncertainty rather than hallucinate.

## Known failure modes

- Query too short (< 2 chars) or too long (> 500 chars) → validation error
- Requested source not in allowed enum → schema validation error
- No relevant passages found in specified sources → empty passages array
- LLM synthesis unavailable if server lacks LLM key → synthesis field absent or error
- Upstream source (arXiv, World Bank, etc.) temporarily unavailable → partial results or timeout
- Payment not completed via x402 protocol → 402 response before query is processed

## How this service works

Answer from TRUSTED sources only (Wikipedia, Wikidata, arXiv, Crossref/DOI, World Bank): returns passages with URL, reliability tier and retrieval time for citation. With synthesize=true you also get an LLM answer that cites the passages and admits when they don't contain the answer.

## Output

Returns a JSON object with an array of passages, each containing a snippet, title, source name, URL, reliability tier integer, and ISO retrieval timestamp. If synthesize=true and an LLM key is available, also returns an LLM-generated answer that inline-cites the passages and explicitly states when the sources do not contain sufficient information.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "query"
     ],
     "properties": {
      "query": {
       "type": "string",
       "maxLength": 500,
       "minLength": 2,
       "description": "Question or topic"
      },
      "sources": {
       "type": "array",
       "items": {
        "enum": [
         "wikipedia",
         "wikidata",
         "arxiv",
         "crossref",
         "worldbank"
        ],
        "type": "string"
       },
       "default": [
        "wikipedia",
        "wikidata",
        "arxiv",
        "crossref"
       ]
      },
      "language": {
       "type": "string",
       "default": "en",
       "maxLength": 10,
       "description": "Wikipedia language edition (en, es, de, fr, pt, ...)"
      },
      "synthesize": {
       "type": "boolean",
       "default": true,
       "description": "Return a cited answer synthesized by an LLM (when the server has an LLM key)"
      },
      "maxPassages": {
       "type": "integer",
       "default": 6,
       "maximum": 20,
       "minimum": 1
      }
     },
     "additionalProperties": false
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "ms": {
       "type": "integer"
      },
      "ok": {
       "type": "boolean"
      },
      "tool": {
       "type": "string"
      },
      "result": {
       "type": "object",
       "properties": {
        "passages": {
         "type": "array",
         "items": {
          "type": "object",
          "properties": {
           "url": {
            "type": "string"
           },
           "tier": {
            "type": "integer"
           },
           "title": {
            "type": "string"
           },
           "source": {
            "type": "string"
           },
           "snippet": {
            "type": "string"
           },
           "retrievedAt": {
            "type": "string"
           }
          }
         }
        }
       }

… (truncated)
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "passages": [
   {
    "url": "https://en.wikipedia.org/wiki/List_of_HTTP_status_codes",
    "tier": 1,
    "title": "List of HTTP status codes",
    "source": "wikipedia",
    "snippet": "...",
    "retrievedAt": "2026-09-07T00:00:00Z"
   }
  ]
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/toll402-trusted-source-lookup-synthesis-c830f40c/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from toll402.dev](https://www.zero.xyz/host/toll402.dev/llms.txt)