Debug Fix beginner · 3 min read

Mistral API error codes reference

Q: Mistral API error codes reference

The Mistral API returns standard HTTP error codes such as 400 for bad requests, 401 for unauthorized access, 429 for rate limiting, and 500 for server errors. Handling these errors requires checking the response status and implementing retries or correcting request parameters accordingly.

Quick answer

The Mistral API returns standard HTTP error codes such as 400 for bad requests, 401 for unauthorized access, 429 for rate limiting, and 500 for server errors. Handling these errors requires checking the response status and implementing retries or correcting request parameters accordingly.

ERROR TYPE api_error

⚡ QUICK FIX

Add exponential backoff retry logic around your API call to handle RateLimitError automatically.

Why this happens

The Mistral API can return errors due to invalid requests, authentication failures, rate limits, or internal server issues. For example, sending a malformed JSON payload or missing required parameters triggers a 400 Bad Request. Using an invalid or expired API key results in a 401 Unauthorized. Exceeding the allowed request rate causes a 429 Too Many Requests. Server-side problems lead to 500 Internal Server Error.

Typical error output looks like:

{"error": {"code": 429, "message": "Rate limit exceeded"}}

python

from mistralai import Mistral
import os

client = Mistral(api_key=os.environ["MISTRAL_API_KEY"])

# Example causing a rate limit error by rapid repeated calls
for _ in range(100):
    response = client.chat.completions.create(
        model="mistral-large-latest",
        messages=[{"role": "user", "content": "Hello"}]
    )
    print(response.choices[0].message.content)

output

Traceback (most recent call last):
  ...
mistralai.errors.RateLimitError: Rate limit exceeded

The fix

Implement error handling with try-except blocks and add exponential backoff retries for RateLimitError. Validate request payloads to avoid 400 errors and ensure your API key is correct to prevent 401 errors.

python

from mistralai import Mistral, errors
import os
import time

client = Mistral(api_key=os.environ["MISTRAL_API_KEY"])

max_retries = 5
retry_delay = 1

for attempt in range(max_retries):
    try:
        response = client.chat.completions.create(
            model="mistral-large-latest",
            messages=[{"role": "user", "content": "Hello"}]
        )
        print(response.choices[0].message.content)
        break
    except errors.RateLimitError:
        print(f"Rate limit hit, retrying in {retry_delay} seconds...")
        time.sleep(retry_delay)
        retry_delay *= 2  # exponential backoff
    except errors.AuthenticationError:
        print("Invalid API key. Check your MISTRAL_API_KEY environment variable.")
        break
    except errors.BadRequestError as e:
        print(f"Bad request: {e}")
        break
    except Exception as e:
        print(f"Unexpected error: {e}")
        break

output

Hello! How can I assist you today?

Preventing it in production

Use robust retry logic with exponential backoff for transient errors like 429 and 500. Validate inputs before sending requests to avoid 400 errors. Monitor API usage to stay within rate limits. Securely store and rotate API keys to prevent 401 errors. Implement logging and alerting to detect and respond to errors quickly.

Related errors

Error	Cause	Quick fix
400 Bad Request	Malformed request or invalid parameters	Validate and correct request payload
401 Unauthorized	Invalid or missing API key	Check and set correct API key in environment
429 Too Many Requests	Exceeded rate limits	Add exponential backoff retries
500 Internal Server Error	Server-side issue	Retry after delay or contact support

✅

Key Takeaways

Handle RateLimitError with exponential backoff retries to avoid request failures.
Validate request data and API keys to prevent 400 and 401 errors.
Monitor usage and implement logging to detect and respond to API errors promptly.

Verified 2026-04 · mistral-large-latest

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