> ## Documentation Index
> Fetch the complete documentation index at: https://docs.autheo.com/llms.txt
> Use this file to discover all available pages before exploring further.

# JSON-RPC error codes

> Standard and Autheo-specific JSON-RPC error codes and how to handle them.

JSON-RPC errors are returned as objects with a `code` and `message` field inside the `error` key of the response.

```json theme={null}
{
  "jsonrpc": "2.0",
  "id": 1,
  "error": {
    "code": -32601,
    "message": "Method not found"
  }
}
```

## Standard JSON-RPC error codes

| Code                 | Name             | Description                                 |
| -------------------- | ---------------- | ------------------------------------------- |
| `-32700`             | Parse error      | Invalid JSON was received                   |
| `-32600`             | Invalid request  | The JSON is not a valid request object      |
| `-32601`             | Method not found | The method does not exist or is unsupported |
| `-32602`             | Invalid params   | Invalid method parameters                   |
| `-32603`             | Internal error   | Internal JSON-RPC server error              |
| `-32000` to `-32099` | Server error     | Implementation-defined server errors        |

## Ethereum execution errors

| Code     | Message                                      | Description                                                                |
| -------- | -------------------------------------------- | -------------------------------------------------------------------------- |
| `-32000` | `execution reverted`                         | Contract execution reverted — check the `data` field for the revert reason |
| `-32000` | `insufficient funds for gas * price + value` | Sender balance too low                                                     |
| `-32000` | `nonce too low`                              | Transaction nonce is lower than the account's current nonce                |
| `-32000` | `nonce too high`                             | Transaction nonce is too far ahead of the current nonce                    |
| `-32000` | `gas limit reached`                          | Block gas limit exceeded                                                   |
| `-32000` | `already known`                              | Transaction already in mempool                                             |

## Decoding revert reasons

When a transaction reverts, the `data` field may contain an ABI-encoded revert reason:

```javascript theme={null}
import { ethers } from "ethers";

try {
  await contract.myFunction(args);
} catch (err) {
  if (err.data) {
    // Try to decode as a standard Error(string) revert
    try {
      const decoded = ethers.toUtf8String("0x" + err.data.slice(138));
      console.error("Revert reason:", decoded);
    } catch {
      console.error("Raw revert data:", err.data);
    }
  }
}
```

## Common causes and fixes

| Error                       | Likely cause                                 | Fix                                                 |
| --------------------------- | -------------------------------------------- | --------------------------------------------------- |
| `-32601 Method not found`   | Method not supported by this node            | Check [supported methods](/apis/json-rpc/overview)  |
| `-32000 execution reverted` | Contract `require()` or `revert()` triggered | Simulate with `eth_call` first to get revert reason |
| `-32000 insufficient funds` | Low balance                                  | Fund the sender account                             |
| `-32000 nonce too low`      | Stale nonce in client                        | Refresh nonce with `eth_getTransactionCount`        |