Learn / Agentic Orchestration / API Fundamentals

API Fundamentals

12 min understand 4 sections
Step 1 of 4

WHY WHY This Matters

Every AI application—from ChatGPT to custom enterprise tools—runs on APIs. Understanding APIs is the bridge between using off-the-shelf tools and building custom solutions. You need API knowledge to:

  • Configure integrations that automation tools provide
  • Debug problems when AI workflows break
  • Evaluate vendors and understand their capabilities
  • Collaborate with developers effectively
  • Build more sophisticated AI applications

You don't need to write code, but you need to speak the language.

Step 2 of 4

WHAT WHAT You Need to Know

What is an API?

The Request-Response Cycle

┌─────────────┐                  ┌─────────────┐
│   CLIENT    │   ──Request──>   │   SERVER    │
│  (your app) │                  │  (AI API)   │
│             │   <──Response──  │             │
└─────────────┘                  └─────────────┘

Request components:

Component Purpose Example
Endpoint URL to call https://api.openai.com/v1/chat/completions
Method Type of action POST (send data), GET (retrieve data)
Headers Metadata Authentication, content type
Body The actual data Your prompt, parameters

Response components:

Component Purpose Example
Status code Success/failure 200 (OK), 400 (bad request), 500 (server error)
Headers Response metadata Rate limit info, content type
Body The actual data AI response, usage stats

Authentication

Authentication patterns:

Pattern Usage Example
API Key Most common OpenAI, Anthropic, Google
Bearer Token OAuth flows Google Cloud, Microsoft
Basic Auth Legacy systems Username + password encoded

AI API Request Structure

A typical AI API request (simplified):

{
  "model": "gpt-4o",
  "messages": [
    {"role": "system", "content": "You are a helpful assistant"},
    {"role": "user", "content": "Explain APIs simply"}
  ],
  "temperature": 0.7,
  "max_tokens": 500
}

Key parameters:

Parameter Purpose Impact
model Which AI model Capability, cost, speed
messages Conversation history Context for response
temperature Randomness (0-1) Creativity vs. consistency
max_tokens Response length limit Cost, completeness
top_p Probability threshold Alternative to temperature
stop Stop sequences Control response endings

AI API Response Structure

A typical response (simplified):

{
  "id": "chatcmpl-abc123",
  "object": "chat.completion",
  "model": "gpt-4o",
  "choices": [
    {
      "message": {
        "role": "assistant",
        "content": "An API is like a waiter..."
      },
      "finish_reason": "stop"
    }
  ],
  "usage": {
    "prompt_tokens": 25,
    "completion_tokens": 150,
    "total_tokens": 175
  }
}

What to look for:

Field Importance
choices[0].message.content The actual AI response
finish_reason Why it stopped (stop, length, error)
usage Token counts for billing/limits

Error Handling

Error handling strategies:

Error Type Strategy
400 errors Fix your request
401/403 errors Check API key
429 errors Wait and retry, use backoff
500/503 errors Retry, fall back to alternative

Key Concepts

Key Concept

api

An API (Application Programming Interface) is a structured way for software to communicate. Think of it like a restaurant:

  • Menu: The API documentation (what you can order)
  • Order: Your API request (what you want)
  • Kitchen: The server processing your request
  • Food: The API response (what you get back)

You don't need to know how the kitchen works—you just need to know how to read the menu and place an order.

Key Concept

api authentication

API authentication proves you're authorized to use the service. Most AI APIs use API keys:

Authorization: Bearer sk-your-api-key-here

Key security rules:

  • Never share your API key publicly
  • Don't commit keys to code repositories
  • Use environment variables or secret managers
  • Rotate keys periodically
  • Monitor for unauthorized usage
Key Concept

api errors

APIs communicate problems through status codes and error messages:

Code Meaning Common Cause
400 Bad Request Malformed input
401 Unauthorized Invalid API key
403 Forbidden Key lacks permission
404 Not Found Wrong endpoint
429 Rate Limited Too many requests
500 Server Error Provider issue
503 Service Unavailable Temporary outage
Step 3 of 4

HOW HOW to Apply This

Exercise: Read API Documentation

API Terminology Quick Reference

Term Definition
Endpoint URL where API lives
Request What you send to API
Response What API sends back
Header Metadata for request/response
Body Main content of request/response
JSON Data format for API communication
Status code Numeric response indicator
Rate limit How often you can call API
Token Unit of text for AI processing
Latency Time for API to respond

Self-Check

Practice Exercises

Review the documentation for a major AI API and answer these questions.

Choose one:

Answer:

  1. What is the endpoint URL for chat completions?
  2. How is authentication handled?
  3. What parameters are required vs. optional?
  4. What models are available and how do they differ?
  5. What are the rate limits?
  6. How is usage billed?
  7. What do the error codes mean?
Step 4 of 4

GENERIC Up Next

In Module 3.3: Automation Platforms, you'll learn how to connect AI APIs to other tools using no-code automation platforms—building workflows that run without manual intervention.

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