What approaches and principles do you use when developing API interfaces?

When developing APIs, I adhere to the following principles:

• RESTful approach: using standard HTTP methods (GET, POST, PUT, DELETE) and a clear URL structure.
• Idempotency and security: methods that should not change the state only perform read operations (GET), while modifying methods handle repeated requests correctly.
• Clear documentation: using OpenAPI/Swagger to describe interfaces.
• Error handling: returning understandable and standardized error codes and messages.
• API versioning: to avoid breaking clients during updates.
• Authentication and authorization: for example, via OAuth or JWT.

Example of a simple Flask API:

from flask import Flask, jsonify, request
app = Flask(__name__)

items = {1: 'item1', 2: 'item2'}

@app.route('/items/<int:item_id>', methods=['GET'])
def get_item(item_id):
    item = items.get(item_id)
    if item:
        return jsonify({'id': item_id, 'name': item}), 200
    else:
        return jsonify({'error': 'Item not found'}), 404

if __name__ == '__main__':
    app.run()