Yes, it is very common to pass parameters in API requests and responses. Parameters allow the API client to specify additional data or filters for the request, and allow the API to return dynamic data based on the request. Here are some key ways parameters are used in APIs:
Query Parameters
For GET requests, parameters are most commonly passed as query parameters in the URL. For example:
https://api.example.com/users?limit=10&offset=50
Here “limit” and “offset” are query parameters that indicate the API should return 10 users starting from the 50th user. This allows fetching specific subsets of data.
Request Body Parameters
For POST, PUT, and PATCH requests, parameters are commonly passed in the request body, typically JSON encoded. For example:
{
"name": "John Doe",
"email": "[email protected]"
}
Here the request body contains parameters for creating a new user in the system.
Route Parameters
Parameters can also be passed in the API route URL itself like:
https://api.example.com/users/{userId}
Where {userId} is a route parameter that identifies which specific user resource to access.
Benefits of Parameters
Passing parameters in API requests allows:
- Fetching specific resource subsets, like pagination
- Filtering, sorting, and querying data
- Specifying fields, expand values, and other options
- Passing data for create/update operations
- Parameterizing routes to access specific resources
Overall, parameters enable APIs to be far more flexible and reusable across a variety of use cases.
Parameter Data Types
Parameters can take on different data types, like:
- Strings – for freeform text, emails, names, etc.
- Integers – for numeric IDs, counts, rates, etc.
- Booleans – for true/false or yes/no values
- Dates – date/time values
- Enums – predefined constant values
The API documentation usually specifies the parameter names, types, format, allowed values, whether they are required or optional, and other information to help developers use the parameters correctly.
Where to Define Parameters?
Parameters can be defined in a few places:
- In the URL query string for GET requests
- In the request body for POST, PUT, PATCH requests
- In the API route URL path for route parameters
- In headers for some special cases
The API documentation will outline where each parameter should be passed to make it work correctly.
Parameter Best Practices
Some best practices for working with API parameters:
- Use camelCase for parameter names
- Make parameters optional where possible, avoid unnecessary required params
- Set parameter type, format, allowed values, default values in docs
- Use arrays for multi-value params like id=[1,2,3]
- Group related parameters together in objects
- Make query params matching API names, not UI terms
Examples of Common Parameters
Here are some examples of common parameters you may find in APIs:
| Parameter | Description |
|---|---|
| limit | Max number of items to return |
| page | Page number for pagination |
| sort | Sort order (asc/desc) |
| filter | Filter items by some criteria |
| fields | Specify fields to return |
| expand | Expand nested objects |
Conclusion
Parameters are a key part of API design that enable flexible, reusable, and discoverable APIs. They allow encapsulating data, options, and filters that control API behavior in a simple way without changing endpoint URLs. Following API best practices for parameter naming, formatting, and documentation ensures parameters are easy to use correctly. Parameters unlock many diverse API use cases without the overhead of creating customized endpoints for each scenario.