How to Call an API and Choose an API Platform

We’ve covered core concepts like API, Token, and Temperature. Now it’s time for the practical part: How to actually call an API?

Many people think APIs are mysterious, but once you grasp a few key elements, calling an API is as simple as online shopping. This chapter will guide you step by step.

Three Core Elements of Calling an API

No matter what tool or platform you use, calling an AI API requires these three things:

1. API Key

API Key = Your ID

Just like you need a bank card PIN to withdraw money, calling an API requires an API Key to prove “This is me, you can serve me.”

What does an API Key look like?

It’s usually a long string of letters and numbers, for example:

sk-REPLACE_WITH_YOUR_API_KEY

Important Reminder:

API Keys are private; do not share them with others.
If someone gets your key, they can use your account to call APIs (spending your money).
If you accidentally leak it, immediately delete the old key on the platform and generate a new one.

2. Base URL

Base URL = The restaurant’s address

When you order food delivery, you need to know where the restaurant is. When calling an API, you need to know where the server is.

Common Base URLs:

OpenAI: https://api.openai.com/v1
Anthropic Claude: https://api.anthropic.com/v1
Google Gemini: https://generativelanguage.googleapis.com/v1
DeepSeek: https://api.deepseek.com/v1

Third-party platforms have different URLs, but the format is similar.

3. Model Name

Model Name = The dish you want to order

At a restaurant, you say “I want braised pork.” When calling an API, you say “I want to use GPT-5.2.”

Common Model Names:

OpenAI: gpt-5.2, gpt-5.2-chat-latest
Claude: claude-opus-4.5, claude-sonnet-4.5
Gemini: gemini-3-pro, gemini-3-flash
DeepSeek: deepseek-chat, deepseek-coder

A Complete API Call Example

Combine these three things, and the simplest API call looks like this:

import openai

# 1. Set the API Key
openai.api_key = "sk-proj-YOUR_API_KEY"

# 2. Set the Base URL (if you use a third-party platform)
openai.base_url = "https://api.openai.com/v1"

# 3. Call the selected model
response = openai.chat.completions.create(
    model="gpt-5.2",  # Model Name
    messages=[
        {"role": "user", "content": "Hello"}
    ]
)

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

Looks complicated? Don’t worry, the platforms introduced later have simpler methods.

Official API vs Third-Party Platforms

Before introducing specific platforms, let’s clarify an important concept: What is the difference between official APIs and third-party platforms?

Official API

Official API = Buying directly from OpenAI, Anthropic, Google

Advantages:

Best stability, direct connection to official servers
Full features, new features supported immediately
Highest security, data does not pass through third parties

Disadvantages:

Requires a foreign credit card
Requires a VPN to access (ChatGPT, Claude, Gemini)
Relatively higher prices
Registration may have barriers

Third-Party Platforms

Third-Party Platforms = Buying from resellers

Third-party platforms first buy API quotas from official sources and then resell them to you.

Advantages:

Supports domestic payments (Alipay, WeChat Pay, UnionPay)
No VPN required
Usually have Chinese interface and customer service
One platform can call multiple AIs (OpenAI, Claude, Gemini, etc.)
Some platforms offer free credits

Disadvantages:

Stability may not be as good as official
Prices may be slightly higher than official (but some are cheaper)
Security requires trusting the platform
Feature updates may lag behind official

Which Should You Choose?

Choose official if you:

Have a foreign credit card
Have a stable VPN
Value data security
Need the latest features

Choose third-party if you:

Don’t have foreign payment methods
Don’t have a VPN
Want to use domestic payments
Want to call multiple AIs from one platform

Platform Recommendations (2 Domestic + 2 International)

Below are four API platforms I recommend, two domestic and two international, covering different needs.

1. DeepSeek Official (Domestic, Official Platform)

Website: https://platform.deepseek.com

Platform Type: Official Platform

Why Recommend?

Official platform, stable and reliable
DeepSeek V3.2 performance is close to GPT-5
Fast access in China, no VPN needed
Simple registration, just a phone number
Extremely low price, great value

Steps to Get API Key:

Open https://platform.deepseek.com
Click “Login/Register” in the top right corner
Register an account with your phone number
After logging in, click “API Keys” on the left
Click “Create API Key”
Copy the key (it is only shown once, so save it)
Click “Interface Documentation” on the left to view the URL and model name

Call Parameters:

Base URL: https://api.deepseek.com
Model Name: deepseek-chat (chat), deepseek-reasoner (reasoning)
API Key: The key you just copied

2. Volcano Engine (Domestic, Official Platform + Third-Party)

Website: https://console.volcengine.com/ark

Platform Type: Official Platform (under ByteDance)

Why Recommend?

ByteDance official platform, stable and reliable
Supports Doubao series models
Supports domestic payments (Alipay, WeChat Pay, UnionPay)
Affordable, great value
Besides Doubao’s own models, you can also call many domestic open-source models like DeepSeek V3.2, GLM 4.7

Usage Steps:

Open https://console.volcengine.com/ark
Register a Volcano Engine account with your phone number
Enter the “Ark Large Model” console
Complete real-name authentication (requires ID)
Click “API Key Management”
Create a new API key
Copy and save the key
Click “Activation Management” on the left, select the model you want to use
On the new page, copy the model name you need (note: the same model may have different names on different platforms, so check carefully)
Go back to the Activation Management page, check if the status is “Activated”, otherwise click on the right to activate model permissions

Call Parameters:

Base URL: https://ark.cn-beijing.volces.com/api/v3
Model Name: doubao-pro-32k, doubao-lite-32k, etc.
API Key: The key you created

New User Benefits:

Free credits upon registration
You can also participate in the activity shown above the screenshot to get more free credits. I have more than enough every day.

3. Google AI Studio (International, Official Platform)

Website: https://aistudio.google.com

Platform Type: Official Platform

Why Recommend?

Google official platform
Free credits available (with limits)
Gemini 3 top-tier performance
Stable and reliable
Supports extremely long context (2 million tokens)
Can be used for free directly in the web interface, no coding required

Also, How to Use the Web Version for Free

If you don’t want to write code, Google AI Studio offers a very convenient web chat interface where you can directly use models like Gemini 3 Pro and Gemini 3 Flash. It’s essentially like being a paid Gemini user.

Usage Steps:

Open https://aistudio.google.com
Log in with your Google account (VPN required)
Click “Playground” on the left
In the top right, select a model:
- gemini-3-pro: Best model, suitable for complex tasks
- gemini-3-flash: Fast model, suitable for daily conversations
- Other experimental models available
Type your question directly in the input box, then click “Run”, and the AI will answer

Advanced Features (Web Version):

1. Upload Files

Click the + icon on the right side of the input box
You can upload images, PDFs, documents, etc.
Supports multimodal understanding

2. Adjust Parameters

On the right, you can adjust the parameters introduced earlier
You can adjust:
- Temperature (creativity)
- Top P
- Max output tokens
- Safety settings

Advantages of the Web Version:

No coding required
No software installation needed
Use directly in the browser
User-friendly interface, full features
Suitable for quick testing and daily use

Who is the web version for?

Complete beginners who can’t code
Those who want to quickly test Gemini’s capabilities
Daily chatting and asking questions
Handling multimodal tasks like documents and images

Get API Key (For Advanced Users)

Back to the main topic, here’s how to get an API Key.

Steps to Get API Key:

On the AI Studio page, click “Get API Key” on the left
Click “Create API Key”
Create and copy the generated API Key
Go back to Playground, select and copy the model name on the right

Call Parameters:

Base URL: https://generativelanguage.googleapis.com/v1beta
Model Name: gemini-3-flash-preview
API Key: The key you copied

Free Tier Limits

Important note! Google AI Studio uses the free tier by default, with the following limits (as of January 2026), and these limits are subject to change:

Requests per minute (RPM): 15
Requests per day (RPD): 1500
Tokens per minute (TPM): 1 million tokens

See detailed limits at: https://ai.google.dev/gemini-api/docs/rate-limits?hl=en

Is the free tier enough?

Web chat: More than enough
Occasional API calls: Sufficient
Heavy automated calls: May not be enough

How to Remove Limits? Link Your Cloud Credits

Google Cloud offers $10 in free credits to new users. After linking it to AI Studio, you can unlock higher limits. For details on how to set up a Google Cloud account, search for “Google Cloud free credits” online—there are many tutorials. We won’t cover that here.

Linking Steps:

In AI Studio, go back to the API interface and click “Set up billing”
Link the Google Cloud billing account you created earlier

Benefits after linking:

Rate limits significantly increased (RPM up to 1000+)
Free credits still valid
$10 can last a long time with the powerful flash model
Both web version and API enjoy higher quotas

4. OpenRouter (International, Third-Party Platform)

Website: https://openrouter.ai

Platform Type: Third-Party Platform

Why Recommend?

One platform to call all major AIs (GPT, Claude, Gemini, etc.)
Transparent pricing, sometimes cheaper than official
Supports Alipay payment (friendly for Chinese users)
Supports credit card and cryptocurrency payments
Free models available for trial
Can call almost every available model
Rankings are convincing

Steps to Get API Key:

Open https://openrouter.ai
Click “Sign In” in the top right corner, log in with Google or GitHub
After logging in, click your avatar in the top right corner and select “Keys”
Click “Create Key”
Give the key a name and click create
Copy the generated key
Search for the model you want in the search box, then copy the name

Call Parameters:

Base URL: https://openrouter.ai/api/v1
Model Name:
- GPT-5.2: openai/gpt-5.2
- Claude Opus 4.5: anthropic/claude-opus-4.5
- Gemini 3 Pro: google/gemini-3-pro
- Free model: meta-llama/llama-3.1-8b-instruct:free
API Key: The key you created

Top-up Methods:

Alipay (most convenient)
Credit card
Cryptocurrency (USDC, etc.)

Price Advantage:

Some models are 10-20% cheaper than official
Transparent pricing, see prices directly on the website
Different providers compete, you choose the cheapest

Free Options:

Some models are completely free (marked with :free)
New users get free credits to try
You can test with free models first

Model Rankings

On the Rankings page, you can see the platform’s model call data; the rankings are very convincing.

Other Free Platforms

Due to space limitations, here are a few other platforms you can use for free:

Cerebras (Ultra-Fast Inference)

Website: https://cloud.cerebras.ai

Features:

Extremely fast inference (claims to be the fastest in the world)
Offers free Llama model calls
Simple registration, just log in with GitHub

NVIDIA NIM (NVIDIA Official)

Website: https://build.nvidia.com

Features:

NVIDIA’s official AI platform
Offers multiple free models
Suitable for testing and development

Both platforms offer free credits. If you’re interested, you can sign up and try them out.

Summary

Three Core Elements:

API Key
Base URL
Model Name

Four Recommended Platforms:

DeepSeek Official (Official) - Best low-cost choice in China
Volcano Engine (Official + Third-Party) - Domestic platform, can call most domestic open-source models
Google AI Studio (Official) - Best free choice internationally (with Cloud Credits), can be used directly in the web
OpenRouter (Third-Party) - All-in-one platform, supports Alipay