APIs and JSON

This is optional enrichment. It helps connect the syllabus concept to real systems, but it is outside H2 exam-core scope unless a question explicitly gives this context.

APIs and JSON are important in modern web applications, cloud services, and software agents. For H2 Computing, the core idea is structured client-server communication, not memorising API products or advanced API design.

The goal is to understand the idea: applications can exchange structured data using HTTP requests and JSON responses. You do not need to memorise real API products, authentication schemes, REST theory, or JavaScript frameworks for H2 Computing.

Beginner Mental Model

A normal web page request often returns HTML for a browser to display.

An API request often returns data for a program to process.

Browser page request:
client asks for page -> server returns HTML -> browser displays page
 
API data request:
program asks for data -> server returns JSON -> program reads values

Caption: An API request and response travel using HTTP; JSON is a common format for the structured data carried in the message body.

What Is an API?

API means application programming interface.

For this note, think of a web API as a controlled way for one program to ask another system for data or action.

Examples:

Situation	API-style meaning
weather app shows forecast	app asks a weather service for structured forecast data
school portal loads timetable	front end asks server for timetable records
agent calls a tool	agent sends a structured request and receives structured output
payment page checks status	app asks payment service whether a transaction succeeded

An API is not the same as a visible web page. A web API exposes defined operations or data for software clients to request.

What Is JSON?

JSON stands for JavaScript Object Notation. It is a text format for representing structured data.

Example JSON:

{
  "student": "Aisha",
  "level": "H2 Computing",
  "completed": true,
  "scores": [8, 10, 9]
}

JSON is useful because many programming languages can read and write it.

Basic JSON shapes:

JSON shape	Example	Similar Python idea
object	{"name": "Aisha"}	dictionary
array	[8, 10, 9]	list
string	"H2 Computing"	string
number	42	integer or float
boolean	true, false	True, False
null	null	None

Important syntax details:

• JSON object keys use double quotes;
• JSON strings use double quotes;
• JSON booleans are lowercase true and false;
• JSON uses null, not Python None;
• JSON text must be parsed before a program can safely use it as structured data.

HTTP Request and JSON Response

An HTTP request has a method, a path or URL, headers, and sometimes a body.

Example API request:

GET /api/assignments/42 HTTP/1.1
Host: example.edu.sg
Accept: application/json

Example JSON response body:

{
  "assignment_id": 42,
  "title": "Binary Conversion Practice",
  "due": "2026-07-15",
  "completed": false
}

The response may also include a status code:

Status	Beginner meaning
200 OK	request succeeded
201 Created	new resource was created
400 Bad Request	client sent invalid data
401 Unauthorized	authentication credentials are missing or invalid
403 Forbidden	the server understood the request but refuses access
404 Not Found	requested resource does not exist
500 Internal Server Error	server-side error

Status codes are not JSON values. They are part of the HTTP response. The JSON body is the structured content carried by the response.

GET and POST as Beginner API Actions

For this enrichment note, two common request methods are enough for a beginner model.

Method	Beginner meaning	Example
GET	retrieve data	get one assignment record
POST	send data to create or process something	submit a new answer

Example POST request body:

{
  "student_id": "S1024",
  "question_id": 7,
  "answer": "101101"
}

Possible response:

{
  "accepted": true,
  "mark": 1,
  "feedback": "Correct binary representation of 45."
}

In a Flask app, a form submission and an API request both send data to the server. A common difference is the expected representation of the input or response:

Route type	Input	Output
page route	form values or URL parameters	HTML page
API route	often JSON or query values	often JSON data

Scope reminder: You are not expected to design a REST API, implement authentication protocols, or memorise status-code lists for H2 Computing. Use these examples only to strengthen the request-response mental model.

Reading JSON in Python

Python’s json module can parse JSON text into Python data structures.

import json
 
response_text = """
{
  "assignment_id": 42,
  "title": "Binary Conversion Practice",
  "completed": false,
  "scores": [8, 10, 9]
}
"""
 
data = json.loads(response_text)
 
print(data["title"])
print(data["completed"])
print(sum(data["scores"]))

Expected output:

Binary Conversion Practice
False
27

Notice the conversion:

JSON text	Python value after parsing
false	False
JSON object	dictionary
JSON array	list

Do not treat JSON text as if it were already a Python dictionary. Parse it first.

APIs, Agents, and Tools

When building software agents, APIs and JSON become especially visible.

Simple model:

agent decides what it needs
agent sends structured tool/API request
tool/API returns structured JSON-like result
agent reads fields from the result
agent decides the next step

Example tool-style request:

{
  "tool": "weather_lookup",
  "arguments": {
    "location": "Singapore",
    "date": "2026-07-08"
  }
}

Example tool-style response:

{
  "ok": true,
  "temperature_c": 31,
  "condition": "cloudy"
}

The important computing idea is not the agent product. It is structured communication: both sides must agree on field names, value types, and meaning.

Common Beginner Mistakes

Mistake	Correction
thinking an API is always a visible web page	an API is usually for software to call
confusing HTTP with JSON	HTTP carries the message; JSON is one possible body format
assuming every response is successful	check status code and error body
using field names that do not exist	inspect the actual JSON keys
treating JSON booleans as Python booleans before parsing	parse JSON first
storing secrets inside API request examples	keep API keys and tokens private

Security and Ethics Notes

APIs can expose data, so they need controls.

Risk	Control idea
unauthorised access	authentication and authorisation
too much data returned	only return necessary fields
invalid input	validation before processing
leaked API key	environment variables, access control, key rotation
excessive requests	rate limiting
personal data exposure	privacy-aware design and consent

This connects to H2 topics even though API design itself is enrichment.

How to Use This in Exam Answers

Default H2 answer:

A web application uses HTTP requests and responses between client and server.
Data must be represented in an agreed format so the receiving program can interpret it.

Only mention APIs and JSON if:

• the question gives an API or JSON example;
• you are explaining a real-world extension;
• you are connecting web apps to modern software systems after giving the syllabus answer.

Avoid:

• making JSON part of core character-encoding answers;
• assuming every web app route is an API;
• discussing REST, OAuth, GraphQL, API gateways, or cloud products unless the question supplies them.

Connect Back to Topics

• Web Applications: HTTP request-response, Flask routes, and client-server web apps.
• Data Representation and Character Encoding: structured text data, strings, numbers, booleans, and encoding context.
• Fundamentals of Computer Networks: HTTP protocol, clients, servers, ports, and network communication.

Final Takeaway

APIs and JSON are a modern extension of ideas already in the syllabus:

client-server communication
+ agreed protocol
+ agreed data representation
+ validation and security
= programs that can exchange structured data reliably