Analyzing Requirements and Planning Your API

Now that you have your API project set up in Apidog, it's time to start the design process. Before you start designing endpoints or creating schemas, you need to understand what your API should do and who will use it. This might seem obvious, but skipping this step is one of the most common mistakes in API design.

Requirements analysis is the foundation of good API design. Without clear requirements, you might build endpoints that nobody needs, miss critical features, or create an API that's confusing to use.

In this chapter, we'll learn how to analyze requirements and plan your API structure. We'll use the Pet Store User module as our example throughout, walking through the complete process from requirements to a planned API structure.

1. Why Requirements Analysis Matters

Imagine building a house without blueprints, or cooking a meal without a recipe. You might end up with something, but it probably won't be what you actually need.

The same is true for APIs. Requirements analysis helps you:

Understand the problem you're solving

Identify what features are actually needed

Avoid building unnecessary endpoints

Design an API that users will actually use

Save time by getting it right the first time

What Happens Without Requirements Analysis?

Without proper requirements analysis, you might:

❌ Create endpoints that don't match user needs

❌ Miss important features (like authentication or validation)

❌ Design inconsistent or confusing APIs

❌ Waste time redesigning later

❌ Build features that nobody uses

Example: If you start designing a User API without understanding that users need to log in, you might forget to include authentication endpoints. Then you'd have to redesign everything later.

2. How to Collect and Analyze Requirements

Requirements analysis is a systematic process. Let's break it down into steps:

Step 1: Identify Business Goals

Start by understanding why you're building this API. What problem does it solve?

Example for Pet Store User Module:

Goal: Allow customers to create accounts and manage their information

Problem: Customers need a way to save their preferences, view order history, and maintain their profile

Value: Better customer experience, personalized service, order tracking

Step 2: Determine API Use Cases

Think about how the API will be used. What are the specific scenarios?

Example use cases for User API:

New customer registration: A new user wants to create an account

User login: An existing user wants to log in to access their account

View profile: A logged-in user wants to see their account information

Update profile: A user wants to change their email or phone number

Manage preferences: A user wants to update their newsletter preferences

Account deletion: A user wants to delete their account

Step 3: Identify User Roles and Permissions

Who will use your API, and what can they do?

For Pet Store User API:

Public users (not logged in):

Can create a new account

Can log in

Authenticated users:

Can view their own profile

Can update their own profile

Can manage their preferences

Can log out

Can delete their own account

System/Admin (future consideration):

Might need to view all users (not in initial scope)

Step 4: Understand Data Flow and Business Rules

How does data move through your system? What are the rules?

For User API:

When a user registers, they must provide email, first name, and last name

Email must be unique (no duplicate accounts)

Password should never be returned in API responses

Users can only access their own data

User preferences are optional and have defaults

3. Identifying Core Resources

Once you understand the requirements, the next step is to identify resources—the main entities your API will manage.

What Is a Resource?

A resource is a thing that your API manages. In REST APIs, resources are typically:

Nouns (not verbs)

Things you can create, read, update, or delete

Things that have properties

Examples of resources:

Users

Orders

Products

Pets

How to Extract Resources from Requirements

Look at your use cases and identify the main "things" being managed:

From our User API use cases:

✅ User — the main resource (users create accounts, view profiles, etc.)

❌ "Login" — this is an action, not a resource

❌ "Registration" — this is an action, not a resource

Wait, but what about login? Login is an operation on the User resource, not a resource itself. We'll handle it as a special endpoint.

Resource Relationships

Resources often relate to each other. Understanding these relationships helps you design better APIs.

For Pet Store (beyond User module):

A User can have many Orders (one-to-many)

An Order belongs to one User (many-to-one)

A Pet can have many Tags (many-to-many)

For User module (current scope):

A User has one set of Preferences (one-to-one)

This is a nested object, not a separate resource

4. Determining Required Operations

Now that you know your resources, determine what operations (actions) can be performed on them.

Standard CRUD Operations

For most resources, you'll need CRUD operations:

Operation	HTTP Method	Purpose	Example
Create	POST	Add a new resource	Create a new user
Read	GET	Retrieve a resource	Get user information
Update	PUT/PATCH	Modify a resource	Update user profile
Delete	DELETE	Remove a resource	Delete user account

Special Operations

Beyond CRUD, you might need special operations:

For User API:

Login — authenticate and get a token

Logout — invalidate the session token

These don't fit the standard CRUD pattern, so they get their own endpoints.

Operations for User Resource

Based on our requirements analysis:

Operation	HTTP Method	Endpoint	Description
Create User	POST	`/users`	Register a new user account
Get User	GET	`/users/{id}`	Retrieve user information
Update User	PUT	`/users/{id}`	Update user profile
Delete User	DELETE	`/users/{id}`	Delete user account
Login	POST	`/user/login`	Authenticate and get token
Logout	POST	`/user/logout`	Invalidate session token

Note: Notice that login/logout use /user (singular) instead of /users (plural). This is a common convention for operations that don't operate on a specific resource instance.

5. Planning Endpoint Structure

Now let's map your resources and operations to actual endpoints (URLs).

From Resources and Operations to Endpoints

The mapping is straightforward:

Resource: User
Operations:
  - Create → POST /users
  - Read → GET /users/{id}
  - Update → PUT /users/{id}
  - Delete → DELETE /users/{id}
  - Login → POST /user/login (special operation)
  - Logout → POST /user/logout (special operation)

RESTful Path Design Principles

When designing paths, follow these principles:

Use plural nouns for collections:

✅ /users (collection of users)

❌ /user (unless it's a special operation)

Use path parameters for specific resources:

✅ /users/{id} (specific user)

❌ /users/getById?id=123 (use query params for filtering, not identification)

Keep paths hierarchical:

✅ /users/{id}/orders (orders for a user)

❌ /userOrders?userId=123 (less RESTful)

Use consistent naming:

✅ /users/{id}

❌ /users/{userId} (redundant - we know it's a user ID)

Complete Endpoint List for User Module

Here's our complete endpoint plan:

POST   /users           - Create a new user
GET    /users/{id}      - Get user by ID
PUT    /users/{id}      - Update user
DELETE /users/{id}      - Delete user
POST   /user/login      - User login
POST   /user/logout     - User logout

Endpoint Grouping and Organization

In Apidog, you can organize endpoints using:

Folders — group related endpoints

Tags — categorize endpoints (e.g., "User", "Authentication")

Modules — separate different functional areas

For the User module, we might organize like this:

User Module/
  ├── User Management/
  │   ├── POST /users
  │   ├── GET /users/{id}
  │   ├── PUT /users/{id}
  │   └── DELETE /users/{id}
  └── Authentication/
      ├── POST /user/login
      └── POST /user/logout

6. Identifying Data Requirements

Finally, determine what data each resource needs. What fields are required? What are optional?

Data Requirements for User Resource

Based on our use cases, a User needs:

Required Fields:

id — unique identifier (generated by system)

email — for login and communication (must be unique)

firstName — user's first name

lastName — user's last name

createdAt — when the account was created (generated by system)

Optional Fields:

phone — phone number (for contact)

preferences — user preferences object

newsletter — whether to receive newsletter (boolean)

notifications — whether to receive notifications (boolean)

Authentication Fields:

password — for login (never returned in responses, write-only)

Field Relationships

Some fields relate to each other:

preferences is a nested object within User (not a separate resource)

id and createdAt are read-only (set by system)

password is write-only (never returned)

Data Validation Requirements

Each field needs validation rules:

Field	Type	Validation Rules
`id`	string	Pattern: `usr_[A-Za-z0-9]{16}`, read-only
`email`	string	Valid email format, unique, required
`firstName`	string	Required, max 50 characters
`lastName`	string	Required, max 50 characters
`phone`	string	Optional, E.164 format if provided
`password`	string	Required for creation, write-only, min 8 characters
`preferences.newsletter`	boolean	Optional, default: false
`preferences.notifications`	boolean	Optional, default: true
`createdAt`	date-time	Read-only, ISO 8601 format

7. Putting It All Together: The User API Plan

Let's summarize everything we've planned:

Resources

User — the main resource

Endpoints

POST   /users           - Create user
GET    /users/{id}      - Get user
PUT    /users/{id}      - Update user
DELETE /users/{id}      - Delete user
POST   /user/login      - Login
POST   /user/logout     - Logout

Data Model (Summary)

User object with:

Required: id, email, firstName, lastName, createdAt

Optional: phone, preferences

Authentication: password (write-only)

Authentication

Token required for: GET, PUT, DELETE /users/{id}, and logout

Create and login endpoints are public

8. Key Takeaways

Requirements analysis and planning are essential before you start designing:

Requirements analysis ensures you build what's actually needed

Use cases help you understand how the API will be used

Resources are the main entities your API manages (nouns)

Operations are the actions performed on resources (CRUD + special operations)

Endpoints map resources and operations to URLs

Data requirements define what fields each resource needs

Planning saves time by getting the structure right from the start

Now that you have a clear plan for the User API, you're ready to design the detailed data models and implement them as schemas in Apidog. In the next chapter, we'll learn how to design and implement your data models—creating schemas with the exact structure, types, and validation rules.

Let's continue with Designing and Implementing Data Models.

Analyzing Requirements and Planning Your API

1. Why Requirements Analysis Matters#

What Happens Without Requirements Analysis?#

2. How to Collect and Analyze Requirements#

Step 1: Identify Business Goals#

Step 2: Determine API Use Cases#

Step 3: Identify User Roles and Permissions#

Step 4: Understand Data Flow and Business Rules#

3. Identifying Core Resources#

What Is a Resource?#

How to Extract Resources from Requirements#

Resource Relationships#

4. Determining Required Operations#

Standard CRUD Operations#

Special Operations#

Operations for User Resource#

5. Planning Endpoint Structure#

From Resources and Operations to Endpoints#

RESTful Path Design Principles#

Complete Endpoint List for User Module#

Endpoint Grouping and Organization#

6. Identifying Data Requirements#

Data Requirements for User Resource#

Field Relationships#

Data Validation Requirements#

7. Putting It All Together: The User API Plan#

Resources#

Endpoints#

Data Model (Summary)#

Authentication#

8. Key Takeaways#