Error Handling Guide

Overview

This guide covers how to handle errors from the Cred Protocol API, including common error codes, error response formats, and best practices for building resilient applications.

Error Response Format

All API errors return a JSON response with a detail field:

{
  "detail": "Error message describing the issue"
}

Some errors may include additional fields:

{
  "detail": "Validation error",
  "errors": [
    {
      "field": "address",
      "message": "Invalid Ethereum address format"
    }
  ]
}

HTTP Status Codes

Client Errors (4xx)

Status	Name	Description
400	Bad Request	Invalid request parameters
401	Unauthorized	Missing or invalid API key
402	Payment Required	Authentication required (API key or x402 payment)
403	Forbidden	Insufficient permissions
404	Not Found	Resource not found
422	Unprocessable Entity	Validation error
429	Too Many Requests	Rate limit or credit limit exceeded

Server Errors (5xx)

Status	Name	Description
500	Internal Server Error	Unexpected server error
502	Bad Gateway	Upstream service error
503	Service Unavailable	Service temporarily unavailable
504	Gateway Timeout	Request timed out

Common Errors and Solutions

400 Bad Request

{ "detail": "Invalid Ethereum address format" }

Causes:

Malformed Ethereum address
Invalid ENS name
Missing required parameters

Solutions:

Validate addresses before making requests
Use checksummed addresses when possible
Verify ENS names resolve correctly

import { isAddress } from 'viem';

function validateAddress(address) {
  // Check if it's a valid address or ENS name
  if (isAddress(address)) return true;
  if (address.endsWith('.eth')) return true;
  return false;
}

401 Unauthorized

{ "detail": "Invalid or missing API key" }

Causes:

Missing Authorization header
Invalid API key format
Revoked API key

Solutions:

Ensure header format is Bearer YOUR_API_KEY
Check for typos in the API key
Verify the key hasn’t been revoked
Generate a new key if needed

// Correct format
headers: {
  'Authorization': 'Bearer sk_live_abc123'
}

// Common mistakes
headers: {
  'Authorization': 'sk_live_abc123'  // Missing "Bearer "
  'Api-Key': 'sk_live_abc123'        // Wrong header name
}

402 Payment Required

{
  "error": "authentication_required",
  "message": "This endpoint requires authentication. Choose one of the following methods:",
  "cred_units": 1,
  "options": [
    {
      "method": "api_token",
      "description": "Use an API token from your dashboard",
      "header": "Authorization: Bearer YOUR_API_KEY",
      "cost": "1 Cred Units"
    },
    {
      "method": "x402_payment",
      "description": "Pay per request with USDC (no account required)",
      "price": "$0.01",
      "currency": "USDC",
      "networks": ["base", "base-sepolia", "skale-base", "skale-base-sepolia"]
    }
  ]
}

Causes:

No Authorization header or X-PAYMENT header provided
This is an informational response, not an error

Response Headers:

X-PAYMENT-REQUIRED: Base64-encoded payment requirements for x402-compatible clients (includes options for all enabled networks)

Solutions:

Add an API key: Authorization: Bearer YOUR_API_KEY
Or use x402 payment: Sign a USDC transfer and include in X-PAYMENT header
Supported networks: Base, Base Sepolia, SKALE Base, SKALE Base Sepolia
See Authentication Guide for details

async function handlePaymentRequired(response) {
  if (response.status === 402) {
    const data = await response.json();

    // Option 1: Prompt user to authenticate
    console.log('Authentication options:', data.options);

    // Option 2: If using x402, process payment header
    const paymentRequired = response.headers.get('X-PAYMENT-REQUIRED');
    // ... sign and retry with X-PAYMENT header
  }
}

403 Forbidden

{ "detail": "Insufficient permissions" }

Causes:

Accessing a feature not in your plan
Account restrictions

Solutions:

Check your plan features in the Dashboard
Upgrade your plan if needed
Contact support for account issues

404 Not Found

{ "detail": "Address not found or has no on-chain activity" }

Causes:

Address has never been used on-chain
ENS name doesn’t exist
Incorrect endpoint path

Solutions:

Verify the address exists on Etherscan
Check ENS name resolution
Verify the endpoint URL

async function getScoreWithFallback(address) {
  try {
    const response = await fetch(`${API_URL}/api/v2/score/address/${address}`, {
      headers: { 'Authorization': `Bearer ${API_KEY}` }
    });
    
    if (response.status === 404) {
      // Address has no activity - return a default or handle gracefully
      return { score: null, message: 'No on-chain activity found' };
    }
    
    return response.json();
  } catch (error) {
    throw error;
  }
}

429 Too Many Requests (Rate Limit)

{
  "detail": "Rate limit exceeded",
  "retry_after": 60
}

Causes:

Exceeded requests per minute limit

Solutions:

Implement exponential backoff
Cache responses where possible
Wait for the retry_after period

See Rate Limiting below.

429 Too Many Requests (Credit Limit Exceeded)

{
  "detail": {
    "error": "credit_limit_exceeded",
    "message": "You have reached your monthly limit of 1,000 Cred Units. Your usage resets on day 15 of each month.",
    "plan": "free",
    "monthly_limit": 1000,
    "used": 1000,
    "remaining": 0,
    "period_end": "2024-02-15T00:00:00+00:00",
    "upgrade_url": "https://app.credprotocol.com/dashboard/billing"
  }
}

Causes:

Exceeded monthly Cred Unit allocation

Response Fields:

Field	Description
`error`	Machine-readable error code
`message`	Human-readable explanation
`plan`	Current plan (free, pro, growth)
`monthly_limit`	Total CUs allowed per month
`used`	CUs consumed this billing period
`remaining`	CUs remaining (0 when limit reached)
`period_end`	When credits reset (ISO 8601)
`upgrade_url`	Link to upgrade plan

Solutions:

Wait until period_end for credits to reset
Upgrade your plan for more Cred Units
Optimize API usage by caching responses
Use summary endpoints (lower CU cost) where possible

async function handleCreditLimitError(response) {
  const error = await response.json();

  if (error.detail?.error === 'credit_limit_exceeded') {
    const resetDate = new Date(error.detail.period_end);
    console.log(`Credit limit reached. Resets on ${resetDate.toLocaleDateString()}`);
    console.log(`Upgrade at: ${error.detail.upgrade_url}`);

    // Optionally notify user or disable API calls until reset
    return {
      limitReached: true,
      resetsAt: resetDate,
      upgradeUrl: error.detail.upgrade_url
    };
  }

  throw new Error(error.detail);
}

500 Internal Server Error

{ "detail": "Internal server error" }

Causes:

Unexpected server-side error
Temporary system issue

Solutions:

Retry with exponential backoff
Contact support if the issue persists
Check status page for outages

Implementing Error Handling

Basic Error Handling

async function getScore(address) {
  const response = await fetch(
    `https://api.credprotocol.com/api/v2/score/address/${address}`,
    {
      headers: { 'Authorization': `Bearer ${API_KEY}` }
    }
  );

  if (!response.ok) {
    const error = await response.json();
    
    switch (response.status) {
      case 400:
        throw new Error(`Invalid request: ${error.detail}`);
      case 401:
        throw new Error('Authentication failed. Check your API key.');
      case 404:
        throw new Error('Address not found or has no activity.');
      case 429:
        throw new Error('Rate limit exceeded. Please try again later.');
      default:
        throw new Error(`API error: ${error.detail}`);
    }
  }

  return response.json();
}

With Retry Logic

async function fetchWithRetry(url, options, maxRetries = 3) {
  let lastError;
  
  for (let attempt = 0; attempt < maxRetries; attempt++) {
    try {
      const response = await fetch(url, options);
      
      // Don't retry client errors (except 429)
      if (response.status >= 400 && response.status < 500 && response.status !== 429) {
        const error = await response.json();
        throw new Error(error.detail);
      }
      
      // Retry on rate limit
      if (response.status === 429) {
        const retryAfter = response.headers.get('Retry-After') || 60;
        await sleep(retryAfter * 1000);
        continue;
      }
      
      // Retry on server errors
      if (response.status >= 500) {
        const delay = Math.pow(2, attempt) * 1000; // Exponential backoff
        await sleep(delay);
        continue;
      }
      
      return response.json();
      
    } catch (error) {
      lastError = error;
      
      // Only retry on network errors
      if (error.name !== 'TypeError') throw error;
      
      const delay = Math.pow(2, attempt) * 1000;
      await sleep(delay);
    }
  }
  
  throw lastError;
}

function sleep(ms) {
  return new Promise(resolve => setTimeout(resolve, ms));
}

Python Example

import time
import requests
from requests.adapters import HTTPAdapter
from urllib3.util.retry import Retry

def create_session():
    session = requests.Session()
    
    retries = Retry(
        total=3,
        backoff_factor=1,
        status_forcelist=[500, 502, 503, 504],
        allowed_methods=["GET"]
    )
    
    adapter = HTTPAdapter(max_retries=retries)
    session.mount("https://", adapter)
    
    return session

def get_score(address):
    session = create_session()
    
    response = session.get(
        f'https://api.credprotocol.com/api/v2/score/address/{address}',
        headers={'Authorization': f'Bearer {API_KEY}'}
    )
    
    if response.status_code == 429:
        retry_after = int(response.headers.get('Retry-After', 60))
        time.sleep(retry_after)
        return get_score(address)  # Retry once
    
    response.raise_for_status()
    return response.json()

Rate Limiting

Understanding Usage Limits

API usage is measured in Cred Units (CUs) based on your plan:

Plan	Cred Units/Month	Price
Free	1,000	$0
Pro	50,000	$249/mo
Enterprise	Unlimited	Custom

Handling Rate Limits

class RateLimitedClient {
  constructor(apiKey, requestsPerMinute = 10) {
    this.apiKey = apiKey;
    this.requestsPerMinute = requestsPerMinute;
    this.requestTimes = [];
  }

  async request(endpoint) {
    // Wait if we've hit the rate limit
    await this.waitForRateLimit();
    
    this.requestTimes.push(Date.now());
    
    const response = await fetch(
      `https://api.credprotocol.com${endpoint}`,
      {
        headers: { 'Authorization': `Bearer ${this.apiKey}` }
      }
    );
    
    if (response.status === 429) {
      const retryAfter = parseInt(response.headers.get('Retry-After') || '60');
      await this.sleep(retryAfter * 1000);
      return this.request(endpoint); // Retry
    }
    
    return response.json();
  }

  async waitForRateLimit() {
    const now = Date.now();
    const oneMinuteAgo = now - 60000;
    
    // Remove old request times
    this.requestTimes = this.requestTimes.filter(t => t > oneMinuteAgo);
    
    if (this.requestTimes.length >= this.requestsPerMinute) {
      const oldestRequest = this.requestTimes[0];
      const waitTime = oldestRequest + 60000 - now;
      await this.sleep(waitTime);
    }
  }

  sleep(ms) {
    return new Promise(resolve => setTimeout(resolve, ms));
  }
}

Best Practices

Validate Input

Validate addresses and parameters before making API calls

Use Retries

Implement exponential backoff for transient errors

Cache Responses

Cache successful responses to reduce API calls

Log Errors

Log errors with context for debugging

Logging Example

async function getScore(address) {
  try {
    const data = await fetchScore(address);
    return data;
  } catch (error) {
    console.error('Cred API Error:', {
      address,
      error: error.message,
      timestamp: new Date().toISOString()
    });
    
    // Re-throw or handle gracefully
    throw error;
  }
}

Get Started

Use Cases

Guides

Overview

Error Response Format

HTTP Status Codes

Client Errors (4xx)

Server Errors (5xx)

Common Errors and Solutions

Implementing Error Handling

Basic Error Handling

With Retry Logic

Python Example

Rate Limiting

Understanding Usage Limits

Handling Rate Limits

Best Practices

Validate Input

Use Retries

Cache Responses

Log Errors

Logging Example

​Overview

​Error Response Format

​HTTP Status Codes

​Client Errors (4xx)

​Server Errors (5xx)

​Common Errors and Solutions

​Implementing Error Handling

​Basic Error Handling

​With Retry Logic

​Python Example

​Rate Limiting

​Understanding Usage Limits

​Handling Rate Limits

​Best Practices

Validate Input

Use Retries

Cache Responses

Log Errors

​Logging Example

Overview

Error Response Format

HTTP Status Codes

Client Errors (4xx)

Server Errors (5xx)

Common Errors and Solutions

Implementing Error Handling

Basic Error Handling

With Retry Logic

Python Example

Rate Limiting

Understanding Usage Limits

Handling Rate Limits

Best Practices

Logging Example