# SYNTHORA RPC Nonce Lookup

> SYNTHORA RPC Nonce Lookup is a paid API for AI agents from rpc-nonce.hergertsynthora.com, paid per call via x402, $0.1/call, status unknown (last checked 2026-09-15).

Returns the next pending transaction nonce for an Ethereum address using eth_getTransactionCount (pending)

## Facts

- Endpoint: POST https://rpc-nonce.hergertsynthora.com/service
- Price: $0.1/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/synthora-rpc-nonce-lookup-4de2ba8a
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_dmtpT7nrPB1juqrqnHz70

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 synthora-rpc-nonce-lookup-4de2ba8a -d '<json body>'
```

Example prompt: What's the next pending nonce for Ethereum address 0xAbCd1234... on Base so I can construct my next transaction?

## When to prefer this

Use this endpoint when you need to programmatically retrieve the pending nonce for an Ethereum-compatible address before constructing or signing a transaction, especially when you want Ed25519-signed deterministic responses for auditability, and when operating on chains supported by SYNTHORA's RPC infrastructure. The first 3 calls per wallet are free, making it useful for low-frequency or testing scenarios before committing USDC via x402.

## Known failure modes

- Invalid or malformed Ethereum address returns an error with no charge
- Upstream RPC node failure returns an error with no charge billed
- Unsupported or invalid chain identifier results in an error response
- Missing required fields (address or chain) causes a request validation error

## How this service works

Next pending nonce for an address via eth_getTransactionCount (pending). Deterministic, Ed25519-signed.

## Output

Returns the pending nonce (transaction count) for the given address, cryptographically signed with Ed25519 for integrity, indicating the next sequence number to use for a new transaction on that chain.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "address"
 ],
 "properties": {
  "chain": {
   "type": "string",
   "description": "chain"
  },
  "address": {
   "type": "string",
   "description": "address"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/synthora-rpc-nonce-lookup-4de2ba8a/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from rpc-nonce.hergertsynthora.com](https://www.zero.xyz/host/rpc-nonce.hergertsynthora.com/llms.txt)