How to Correctly Place a Stop-Limit Order Using MEXC API

Question

I'm trying to place a stop-limit order on MEXC using their API, but I keep encountering an error. The error message I'm receiving is:

HTTP error occurred: 400 Client Error: Bad Request for url: https://api.mexc.com/api/v3/order
{"code":700013,"msg":"Invalid content Type."}

Below is the script I am using to place the order:

import requests
import time
import hmac
import hashlib

# Your MEXC API key and secret
API_KEY = 'your_api_key'
API_SECRET = 'your_api_secret'

# Base URL for MEXC API
BASE_URL = 'https://api.mexc.com/api/v3'

# Function to create the signature for the request
def create_signature(query_string, secret):
    return hmac.new(secret.encode(), query_string.encode(), hashlib.sha256).hexdigest()

# Function to place a stop-limit order
def place_stop_limit_order():
    endpoint = '/order'
    timestamp = int(time.time() * 1000)
    
    # Parameters for the stop-limit order
    params = {
        'symbol': 'ETHUSDC',
        'side': 'BUY',
        'type': 'STOP_LOSS_LIMIT',   # Order type
        'quantity': '0.01',         # Quantity to buy
        'price': '4000.01',          # Limit price
        'stopPrice': '4000',         # Stop price
        'timeInForce': 'GTC',        # Time in force
        'timestamp': timestamp
    }

    query_string = '&'.join([f"{key}={value}" for key, value in sorted(params.items())])
    signature = create_signature(query_string, API_SECRET)
    
    headers = {
        'X-MEXC-APIKEY': API_KEY,
        'Content-Type': 'application/x-www-form-urlencoded'  # Correct content type
    }

    # Adding signature to the query string
    query_string += f"&signature={signature}"

    # Make the request to place the order
    response = requests.post(BASE_URL + endpoint, headers=headers, data=query_string)
    try:
        response.raise_for_status()  # Raise an HTTPError for bad responses (4xx and 5xx)
    except requests.exceptions.HTTPError as err:
        print(f"HTTP error occurred: {err}")  # Print HTTP error
        print(response.text)  # Print the response content
    except Exception as err:
        print(f"Other error occurred: {err}")  # Print other errors

    return response.json()

# Main function to place the stop-limit order
def main():
    result = place_stop_limit_order()
    print(f"Order placed: {result}")

if __name__ == "__main__":
    main()

I have ensured that the Content-Type is set to 'application/x-www-form-urlencoded' as suggested in various documentation. Despite this, I still get the invalid content type error.

Could someone please help me identify what I might be doing wrong? Any suggestions or corrections would be greatly appreciated.

Thank you in advance!

Answer 1

Documentation for /api/v3/order shows example

POST /api/v3/order?symbol=MXUSDT&side=BUY&type=LIMIT&quantity=50&price=0.1&timestamp={{timestamp}}&signature={{signature}}

and it means it doesn't send it as form but as query string

and this needs params= instead of data=

response = requests.post(..., params=query_string)

---

Example also doesn't care if parameters are in order so you may send dictionary without converting to string

response = requests.post(..., params=params)