# Synapse API — SEI Transaction History

> Synapse API — SEI 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 addresses on the SEI blockchain network

## Facts

- Endpoint: POST https://synapse-api-brown.vercel.app/api/sei/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-sei-transaction-history-43a03876
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_WklmaVdmhEogEuR_e5-Jq

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-sei-transaction-history-43a03876 -d '<json body>'
```

Example prompt: Pull the last 25 transactions sent from SEI address 0xAbc123... to 0xDef456..., ordered newest first, and include metadata — skip any zero-value transfers.

## When to prefer this

Use this endpoint when you need on-chain transaction history specifically for the SEI blockchain network, with support for address filtering, block range scoping, category filtering, and pagination. Prefer this over generic blockchain explorers when you need programmatic, pay-per-call access without API key registration, or when building automated SEI wallet monitoring or auditing workflows.

## Known failure modes

- Invalid address format returns a 400 or empty result
- Invalid block range (fromBlock > toBlock) may return an error or empty list
- Unknown category values may be silently ignored or cause a 400
- Payment not received (402) if x402 payment header is missing or insufficient
- Rate limiting or timeout if maxCount is very large
- pageKey expiry if too much time passes between paginated calls

## 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 transactions on the SEI blockchain matching the specified filters, including transfer categories, block numbers, sender/receiver addresses, and optionally full transaction metadata. A pageKey is returned when more results exist for subsequent requests.

## 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-sei-transaction-history-43a03876/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)