How to integrate the ChatGPT API into a project

Did you know that in 2025 over 2 million developers use the ChatGPT API To add conversational intelligence to apps, websites and automations? From a simple chatbot on WhatsApp to an internal wizard that summarizes 50-page reports in 10 seconds, the API of openai It allows you to bring the power of GPT-4O, GPT-4O-MINI and O1 to any project with just a few lines of code. And the best: you have 5 $ free when you sign up and the cheapest model costs less than 0,002 € for every 1,000 tokens. If you’ve ever wanted your app to talk, reason, or create content like a human, this is the perfect time to start.

Getting Started: Create your account and get the API key

1. go to https://platform.openai.com/signup And sign up with email or Google/GitHub account. 2 Confirm the mobile (required in Spain). 3 In the dashboard, press “View API Keys” → “Create New Secret Key”. 4 Copy the key (starts with Sk-Live-…) and keep it in a safe place (never upload it to GitHub).

Tip: Activate billing with a card (they don’t charge you until you exceed $5 free) and set spending limits to avoid surprises.

Quick installation according to your language

Python (the most used)

bash

pip install openai

node.js/javascript

bash

npm install openai

php

bash

composer require openai-php/client

Curl (if you don’t want bookstores)

bash

curl https://api.openai.com/v1/chat/completions \
  -H "Authorization: Bearer TU_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{...}'

Minimum functional example in Python (30 seconds)

Python

from openai import OpenAI

client = OpenAI(api_key="sk-...")

respuesta = client.chat.completions.create(
    model="gpt-4o-mini",
    messages=[
        {"role": "system", "content": "Eres un asistente español muy directo y con humor."},
        {"role": "user", "content": "¿Cómo está el tiempo hoy en Madrid?"}
    ],
    temperature=0.7
)

print(respuesta.choices[0].message.content)

Ready! You already have your first bot working.

Models available in November 2025 and which one to choose

Recommendation for 90% of Spanish projects: Start with GPT-4O-MINI. It’s 40 times cheaper than the original GPT-4 and outperforms GPT-3.5 Turbo on almost everything.

Advanced Features You Should Know

Streaming of responses (user sees write in real time)

Python

stream = client.chat.completions.create(
    model="gpt-4o-mini",
    messages=[...],
    stream=True
)
for chunk in stream:
    if chunk.choices[0].delta.content:
        print(chunk.choices[0].delta.content, end="", flush=True)

Function calls and tools (Function Calling)

Allows the model to run code or see External APIs:

Python

def obtener_tiempo(ciudad):
    # Aquí tu lógica o API del tiempo
    return f"En {ciudad} llueve y hace frío."

tools = [
    {
        "type": "function",
        "function": {
            "name": "obtener_tiempo",
            "description": "Devuelve el tiempo actual",
            "parameters": {"type": "object", "properties": {"ciudad": {"type": "string"}}}
        }
    }
]

Upload and analyze files (PDF, images, Excel)

Python

client.files.create(file=open("informe.pdf", "rb"), purpose="assistants")
# Vision con gpt-4o
response = client.chat.completions.create(
    model="gpt-4o",
    messages=[
        {"role": "user", "content": [
            {"type": "text", "text": "¿Qué pone en esta factura?"},
            {"type": "image_url", "image_url": {"url": "https://...jpg"}}
        ]}
    ]
)

Assistants API: Create your own persistent “Jarvis”

Perfect for long projects (technical support, personal tutor, etc.). Includes automatic memory, document recovery and code execution.

good practices and tricks that the pros use

• Use Powerful System Prompts: Spend time on a good initial prompt; Save tokens and improve results.
• Limit max_tokens to avoid eternal answers.
• Implement retries with Exponential Backoff (API can return 429).
• Cache Frequent answers (redis or SQLite).
• Monitor usage in https://platform.openai.com/usage
• Hide your key with environment variables (.env).

Real examples of Spanish projects with ChatGPT API

• Wallapop: Automatic summary of product descriptions.
• Cabify: Internal chatbot that reads payroll PDFs.
• A dental clinic in Valencia: WhatsApp Business with GPT-4O-MINI that schedules appointments and answers questions 24 hours.
• Online education startup: spell checker + personalized explanations.

Realistic Realistic Cost (November 2025)

Complementary tools that make life easier

• Langchain or LlamaIndex → For complex projects with RAG.
• Make.com or Zapier → Integration without code.
• Vercel AI SDK → for next.js in minutes.
• Helicone or Langsmith → Monitoring and debugging.

start with the ChatGPT API It has never been so easy or so cheap. With a free account, a code editor and 10 minutes you can have your first prototype running.

More about ChatGPT

Do you want to master ChatGPT completely? Check our Complete ChatGPT Guide 2026: Prompts, Tutorials and Practical Uses With all the advanced tricks and apps.

→ Access the complete guide here

Sources consulted

• Openai Platform – API Official Documentation → https://platform.openai.com/docs
• Openai Cookbook from Openai (real examples) → https://cookbook.openai.com
• Openai Pricing November 2025 → https://openai.com/api/pricing
• Xataka – Complete ChatGPT API Guide in 2025 → https://www.xataka.com/basics/api-chatgpt-guia-complete
• Genbeta – How to use the OpenAI API in real projects → https://www.genbeta.com/development/como-usar-api-openai-proyectos-reales
• FreeCodeCamp – ChatGPT API Tutorial 2025 → https://www.freecodecamp.org/news/chatgpt-api-tutorial/