# Synapse API — Ethereum Transaction History

> Synapse API — Ethereum Transaction History is a paid API for AI agents from synapse-api-brown.vercel.app, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-14).

Retrieves paginated transaction history for Ethereum addresses, filtered by block range, category, and direction, via pay-per-call x402 billing.

## Facts

- Endpoint: POST https://synapse-api-brown.vercel.app/api/ethereum/tx/history
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/synapse-api-ethereum-transaction-history-8a19d8b1
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Aa0z64oK9MXkKjTw4zTv1

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-api-ethereum-transaction-history-8a19d8b1 -d '<json body>'
```

Example prompt: Fetch all Ethereum transaction history for wallet 0xAbC...123 from block 18000000 to 19000000, sorted ascending, including metadata and excluding zero-value transfers, and return up to 100 results.

## When to prefer this

Choose this endpoint when you need Ethereum-specific historical transaction data with flexible filtering by address, block range, and asset category. It is well-suited for wallet audits, portfolio reconciliation, and on-chain activity analysis where pagination and metadata enrichment matter. Prefer it over generic blockchain explorers when you need programmatic, structured results with pay-per-call economics.

## Known failure modes

- Invalid address format returns a 400 error
- Block range too large may timeout or return partial results
- Unknown category values may cause a 422 validation error
- Exhausted page cursor or invalid pageKey returns empty or error
- Rate limiting or payment failure via x402 returns 402 Payment Required
- No transactions found returns empty array with no error

## How this service works

High-speed API suite for AI processing, web scraping, and smart data utilities across 57+ blockchain networks. Pay-per-call via x402.

## Output

Returns a paginated list of Ethereum transactions matching the specified filters, including transfer categories (ETH, ERC-20, ERC-721, etc.), block numbers, sender/receiver addresses, asset values, and optional metadata. Includes a pageKey for fetching subsequent pages.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "order": {
   "enum": [
    "asc",
    "desc"
   ],
   "type": "string"
  },
  "pageKey": {
   "type": "string"
  },
  "toBlock": {
   "type": "string"
  },
  "category": {
   "type": "array",
   "items": {
    "type": "string"
   }
  },
  "maxCount": {
   "type": "number"
  },
  "fromBlock": {
   "type": "string"
  },
  "toAddress": {
   "type": "string"
  },
  "fromAddress": {
   "type": "string"
  },
  "withMetadata": {
   "type": "boolean"
  },
  "excludeZeroValue": {
   "type": "boolean"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/synapse-api-ethereum-transaction-history-8a19d8b1/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from synapse-api-brown.vercel.app](https://www.zero.xyz/host/synapse-api-brown.vercel.app/llms.txt)