Error Handling

How to handle errors when using Sim APIs

This guide explains how to handle errors when using Sim APIs, including common error codes, troubleshooting steps, and code examples for proper error handling.

Errors vs. Warnings

Sim APIs distinguish between errors and warnings:

• Errors indicate that the request failed and could not be fulfilled. The API returns an error response with an HTTP 4xx or 5xx status code.
• Warnings indicate non-fatal issues where the request was partially fulfilled. The API returns a successful HTTP 200 response with data, but includes a warnings array to inform you about issues that occurred.

When Warnings Occur

Warnings are currently used when you request data for specific chains via the chain_ids parameter and some of those chains are not supported. For example:

• If you request ?chain_ids=1,9999,10 and chain 9999 is not supported, the API will return data for chains 1 and 10, plus a warning about chain 9999.

Warning Response Format

When warnings are present, they appear in a warnings array within the successful (HTTP 200) response:

{
  "wallet_address": "0x37305b1cd40574e4c5ce33f8e8306be057fd7341",
  "balances": [...],
  "warnings": [
    {
      "code": "UNSUPPORTED_CHAIN_IDS",
      "message": "Some requested chain_ids are not supported. Balances are returned only for supported chains.",
      "chain_ids": [9999, 77777777777],
      "docs_url": "https://docs.sim.dune.com/evm/supported-chains"
    }
  ]
}

Each warning includes:

• code: A machine-readable warning code (e.g., UNSUPPORTED_CHAIN_IDS)
• message: A human-readable description of the warning
• chain_ids: The list of chain IDs that caused this warning (for chain-related warnings)
• docs_url: A link to relevant documentation for more information

Error Response Format

Authentication, rate limiting, and quota enforcement errors return JSON with an error field:

{
  "error": "invalid API Key"
}

All other errors return JSON with a message field:

{
  "message": "Internal server error"
}

A few endpoints (EVM Transactions, Activity, Token Info) return errors as plain text with no JSON wrapper. Check the error responses documented on each endpoint’s page for the exact format.

When handling errors programmatically, check for both "error" and "message" fields in the response body.

Common Error Codes

HTTP Status	Description	Troubleshooting
400	Bad request	Verify the address format and other parameters in your request
401	Invalid or missing API key	Check that you’re including the correct API key in the X-Sim-Api-Key header
402	Quota limit exceeded	Your request would exceed your compute unit quota. Contact [e-mail] to upgrade your plan
403	Forbidden	Your API key does not have Sim API permissions. Check your key’s assigned permissions
404	Resource not found	Verify the endpoint URL and resource identifiers
405	Method not allowed	The URL path is valid but the HTTP method is not supported. Use the correct method (e.g. GET)
429	Too many requests	Implement backoff strategies and consider upgrading your plan if you consistently hit limits
500	Internal server error	Retry the request after a short delay; if persistent, contact support
502	Bad gateway	The service is temporarily unreachable. Retry the request after a short delay
503	Service unavailable	The service is temporarily in a retry state. Retry after a short delay

Handling Warnings in Code

When processing API responses, check for the warnings array to be notified of non-fatal issues:

JavaScript

const response = await fetch('https://api.sim.dune.com/v1/evm/balances/0xd8da6bf26964af9d7eed9e03e53415d37aa96045?chain_ids=1,9999,10', {
  headers: {'X-Sim-Api-Key': 'YOUR_API_KEY'}
});

const data = await response.json();

// Check for warnings
if (data.warnings && data.warnings.length > 0) {
  data.warnings.forEach(warning => {
    if (warning.code === 'UNSUPPORTED_CHAIN_IDS') {
      console.warn(`Warning: Chains ${warning.chain_ids.join(', ')} are not supported.`);
      console.warn(`See: ${warning.docs_url}`);
    }
  });
}

// Process the data that was successfully returned
console.log(`Found ${data.balances.length} balances`);

Python

import requests

response = requests.get(
    'https://api.sim.dune.com/v1/evm/balances/0xd8da6bf26964af9d7eed9e03e53415d37aa96045',
    headers={'X-Sim-Api-Key': 'YOUR_API_KEY'},
    params={'chain_ids': '1,9999,10'}
)

data = response.json()

# Check for warnings
if 'warnings' in data and len(data['warnings']) > 0:
    for warning in data['warnings']:
        if warning['code'] == 'UNSUPPORTED_CHAIN_IDS':
            print(f"Warning: Chains {warning['chain_ids']} are not supported.")
            print(f"See: {warning['docs_url']}")

# Process the data that was successfully returned
print(f"Found {len(data['balances'])} balances")

Handling Errors in Code

Here are examples of how to properly handle errors in different programming languages:

JavaScript

fetch('https://api.sim.dune.com/v1/evm/balances/0xd8da6bf26964af9d7eed9e03e53415d37aa96045', {
  method: 'GET', 
  headers: {'X-Sim-Api-Key': 'YOUR_API_KEY'}
})
  .then(async response => {
    if (!response.ok) {
      // Read response as text first, then try to parse as JSON.
      // Some endpoints return JSON errors, others return plain text.
      const text = await response.text();
      let errorMessage;
      try {
        const err = JSON.parse(text);
        errorMessage = err.error || err.message;
      } catch {
        errorMessage = text;
      }
      throw new Error(`API error (${response.status}): ${errorMessage || response.statusText}`);
    }
    return response.json();
  })
  .then(data => {
    console.log('Success:', data);
  })
  .catch(err => {
    console.error('Error:', err);
  });

Python

import requests
import time

def get_balances(address, api_key, max_retries=3):
    url = f"https://api.sim.dune.com/v1/evm/balances/{address}"
    headers = {"X-Sim-Api-Key": api_key}
    
    for attempt in range(max_retries):
        try:
            response = requests.get(url, headers=headers)
            response.raise_for_status()  # Raises an exception for 4XX/5XX responses
            return response.json()
            
        except requests.exceptions.HTTPError as err:
            status_code = err.response.status_code
            error_data = {}
            
            # Parse error body. Some endpoints return JSON, others plain text.
            try:
                error_data = err.response.json()
                error_message = error_data.get('error') or error_data.get('message', 'Unknown error')
            except ValueError:
                error_message = err.response.text or 'Unknown error'
            
            print(f"HTTP Error {status_code}: {error_message}")
            
            # Handle specific error codes
            if status_code == 429:  # Rate limit exceeded
                wait_time = min(2 ** attempt, 60)  # Exponential backoff
                print(f"Rate limit exceeded. Retrying in {wait_time} seconds...")
                time.sleep(wait_time)
                continue
            elif status_code == 500:  # Server error
                if attempt < max_retries - 1:
                    wait_time = 2 ** attempt
                    print(f"Server error. Retrying in {wait_time} seconds...")
                    time.sleep(wait_time)
                    continue
            
            # For other errors or if we've exhausted retries
            return {"error": error_message, "status_code": status_code}
            
        except requests.exceptions.RequestException as err:
            print(f"Request error: {err}")
            return {"error": "Network or connection error", "details": str(err)}
    
    return {"error": "Max retries exceeded"}

# Usage
result = get_balances("0xd8da6bf26964af9d7eed9e03e53415d37aa96045", "YOUR_API_KEY")
if "error" in result:
    print(f"Failed to get balances: {result['error']}")
else:
    print(f"Found {len(result['balances'])} token balances")

Best Practices for Error Handling

1. Always check for errors: Don’t assume API calls will succeed.

2. Use HTTP status codes: Rely on HTTP status codes rather than parsing error message strings for programmatic decisions.

3. Implement retry logic with backoff: For transient errors (like rate limits or server errors), implement exponential backoff.

4. Provide meaningful error messages: Transform API error responses into user-friendly messages.

5. Log errors for debugging: Maintain detailed logs of API errors for troubleshooting.

6. Implement fallbacks: When possible, have fallback behavior when API calls fail.

Debugging Tips

If you’re experiencing persistent errors:

1. Verify your API key: Ensure it’s valid and has the necessary permissions.

2. Check request format: Validate that your request parameters match the API specifications.

3. Inspect full error responses: The error message often contains specific details about what went wrong.

4. Monitor your usage: Check if you’re approaching or exceeding rate limits.

5. Test with cURL: Isolate issues by testing the API directly with cURL:

   curl -v -X GET "https://api.sim.dune.com/v1/evm/balances/0xd8da6bf26964af9d7eed9e03e53415d37aa96045" \
        -H "X-Sim-Api-Key: YOUR_API_KEY"
   

Need More Help?

If you’re still experiencing issues after following these guidelines, please reach out through our support channels.