# Synapse Rerank

> Synapse Rerank is a paid API for AI agents from anibalb.duckdns.org, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-31).

Reranks a list of documents by relevance score given a query, returning ordered results with confidence scores.

## Facts

- Endpoint: GET https://anibalb.duckdns.org/x402/rerank?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-31
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/synapse-rerank-5d922bdc
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_i-qtq7Udau2wJe4nYjGON

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 synapse-rerank-5d922bdc
```

Example prompt: Rerank these five passages by how relevant they are to the question 'What are the side effects of ibuprofen?' and give me back their relevance scores: [passage1, passage2, passage3, passage4, passage5].

## When to prefer this

Choose this endpoint when you need a lightweight, pay-per-call reranker with no account setup, especially in RAG pipelines where you want to rescore retrieved chunks before presenting them to a language model. Prefer it over self-hosted rerankers when you want zero infrastructure overhead and micro-transaction pricing in USDC.

## Known failure modes

- Empty or malformed documents parameter returns an error
- Documents string exceeds length limits causing rejection
- Network timeout on large document sets
- Payment failure via x402 if USDC balance is insufficient
- Malformed JSON in response if service is temporarily degraded

## How this service works

Public data and utility APIs paid per call in USDC on Base (x402). No accounts, no API keys. 174 routes: crypto/equity data, onchain reads, DNS/email/security intel, geo/weather, x402 payment diagnostics, dev utilities and more.

## Output

A JSON array of result objects, each containing the original document index and a relevance_score between 0 and 1, sorted from most to least relevant. Agents can use these scores to reorder or filter their document set.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "documents": {
   "type": "string"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "results": [
   {
    "index": 0,
    "relevance_score": 0.9
   }
  ]
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/synapse-rerank-5d922bdc/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from anibalb.duckdns.org](https://www.zero.xyz/host/anibalb.duckdns.org/llms.txt)