What is API documentation?
API documentation is a set of instructions that explain how to use, or program against an API. In other words, it’s the reference manual for your API.
In many ways, API documentation is similar to an ordinary user manual. So if you’re familiar with how manuals for a consumer product like a washing machine is written, you’ll be able to effectively create API documentation too.
Good API documentation should contain:
- An introduction explaining what the API does and why you should use it
- A summary of all the methods exposed by the API along with examples of input and output for each method
- Detailed technical information about each method such as parameters and return values
- Usage guides that show how to call each method in code snippets written in as many programming languages as possible
- A changelog that documents any changes to the API and the date of those changes
- Version information such as the current version of the API
- Getting started guides that show developers how to install, setup and use your API
- A troubleshooting guide that lists common problems and how to solve them
- A list of related resources, such as user forums or documentation created by other developers
What are API methods and parameters?
For no-coders and those new to APIs and API calls, some of these terms – methods, parameters, etc. – may be foreign to you. We’ll break them down so you can understand how they work.
Methods are the different actions an API can perform, such as updating a database record or sending an email. They are usually exposed through HTTP requests. For instance, if you need to update the status of a ticket in your helpdesk system then you would send a PUT request to the API containing the ticket number and new status code.
Parameters are pieces of data that you provide to an API method to tell it how you want it to be performed. They are added as URL query string values or POST body parameters. For example, if you’re sending a PUT request then your website will need to contain one or more of the following parameters:
ticket_number – The ID of the ticket you’re updating
status – The new status code of the ticket
from_address – Who the ticket is coming from. This can be either an email address or a user ID
to_address – Who the message should be sent to. This can also be either an email address or a user ID.
The primary methods for an API are GET, PUT, POST, and DELETE. Generally speaking, the usage of these methods are pretty straightforward.
- GET – Retrieves data from a database
- PUT – Updates data in a database
- POST – Creates new data (also called “resources”)
- DELETE – Deletes resources from a database. Check to make sure you really want to delete the resource before sending this request!
For GET and DELETE requests, parameters are passed as query string or cookie values. For PUT and POST requests, they are passed as either URL query string or POST body parameters.
There are other less common methods too, such as head, trace, options and connect. There are also secondary HTTP request types like OPTIONS. Those are more advanced than we will cover here.
What are API definitions?
An API definition is a set of instructions that allow software to understand and interact with your programmatic interface. The most commonly used API definition format for defining an API is the OpenAPI Specification (formerly called Swagger) along with its JSON and YAML variants such as RAML (RESTful API Modeling Language).
Each object in an OpenAPI specification describes a resource, which represents a piece of data found in your programmatic interface such as a ticket, user profile, etc. Each resource has one or more methods like GET and POST that can be used to interact with it.
You can give resources and the API as a whole metadata tags like name and version if you want to. When you generate human-readable documentation for your API, this metadata is used to give your API a title, description and version number.
Why API documentation matters
Building a great API is important. However, it’s not enough to just build it and put it out there.
To enjoy the benefits of an active developer community around your API, you need to create amazing API docs to go with it.
A successful API can make developers’ lives easier by enabling them to use cool new technologies in their projects. By providing clear instructions for how to use your API, you are practically guaranteeing that API consumers will be able to do this quickly and easily.
We discuss some more reasons why good documentation matters next.
Great community engagement
APIs only thrive when there’s a thriving developer community behind them. Good documentation helps developers get up and running with your API quickly, leading to better engagement with the platform.
Better search rankings
If a developer is searching for a solution to a problem on Google, and your documentation appears first in the search results, chances are they’ll read more of your docs. If you have clear, helpful documentation that gives them what they’re looking for quickly, it’s more likely that you will get their business.
Fewer support requests
Your products might be great but if people can’t figure out how to use them effectively because there’s no proper documentation, developers will reach out for help. Providing good API docs means fewer questions from frustrated developers who just want to do their jobs.
What are API documentation tools?
An API documentation tool is an application that you can use to build, manage and host your API documentation.
There are several types of API documentation generators – some focus on generating beautiful human-readable output for developers who want to browse your documentation online. Others focus on automatically producing machine-comprehensible code snippets in a range of programming languages which developers can use in their apps.
So which type should you choose? Most API Documentation tools are hybrids, so you can probably find something that suits your needs. However, here are some things to think about when selecting one:
- Which programming languages do you want to support?
- What features do you need? For example, if you want to automatically produce code samples for your documentation, you’ll need a tool that supports this feature.
- Do you want it hosted as part of an existing product? Or do you want to download and install it yourself? This is especially relevant if you’re looking at Open Source options – if don’t have many resources available, or you just want to start fast, it might be more convenient to deploy an existing product.
- How much do you want to spend? Most API Documentation tools are either Open Source or offer a free option. Be sure to check the costs before selecting an option – some require payment plans for certain features, while others offer tiered pricing based on usage limits.
7 Best API Documentation Tools
Now that you understand what API Documentation tools are, and the types of features that they offer, let’s take a look at some of your options for generating documentation.
Backendless allows you to generate API documentation for your API Services in a matter of minutes. Docs are accessible through a URL or as a downloadable file, and Backendless supports several doc types including Swagger and OpenAPI 3.0. Your API documents can be utilized to automate the client-server connection process by streamlining it with external management tools for your Backendless-managed APIs.
- External service management – Backendless generates API documentation that other external service management tools and API providers can read, making your APIs discoverable.
- Multiple doc formats – Backendless creates API documentation in seven different formats for every API Service. Whether you’re using Swagger, OpenAPI 3.0, or API Blueprints, integrating with your API services is a breeze.
- No-Code app builder API integration – Backendless allows you to integrate with your No-Code app builder through the API. Easily add rich APIs and documentation to your applications without any need for technical coding skills.
Stoplight is a complete API documentation tool that allows you to create, organize and share your APIs. Stoplight automatically generates SDKs for any language in minutes – there’s no need to write code or deal with complex build tools.
- API design guides – Stoplight provides a simple way to manage all of your API designs from a single place. You can quickly change parameters, add error handling and parameter samples, then generate the new specification into an OpenAPI 3.0 model where it can be used for mock testing and generating SDKs in multiple languages.
- Crowd tested integrations – Stoplight ensures that your APIs work with more than 1,200 libraries so developers don’t have to manually test them themselves. It also includes API design guidelines for 30+ popular services to help you achieve the best coverage.
- Mock server – Stoplight allows you to create a mock server in minutes using an OpenAPI 3.0 specification (or Swagger definition). You can then share it with other team members or automate testing by publishing the URL so that your CI/CD tools can connect with it.
ReDoc is an Open Source API documentation tool. It produces beautiful, human-readable docs in seconds, with support for both HTML and Markdown formats. You can host them wherever you like or download ReDoc’s official web app to view your documentation on the go.
- Markdown support – ReDoc lets you write your docs in Markdown format, making it simple to create elegant looking pages using a regular text editor. The tool also includes Markdown syntax highlighting and code block rendering (with language specific font selection).
- Server side rendering – ReDoc renders the client side website locally on your development machine before deploying it, so it works even if there are no internet connections available when you’re building apps that need to work offline.
- Offline support – By using service workers, ReDoc is able to keep working offline once it’s been downloaded for the first time, including after updates have been applied.
- Dynamic data – You can use ReDoc to create extensive documentation with dynamic data. This allows you to alter your docs based on environment variables or other conditions so that developers can test different data sets without having to rebuild their docs each time.
Postman is a complete API development environment that allows you to manage APIs and build requests. You can share collections privately with other members of your team, add comments to requests, and use shared environments to test how changes will affect existing code without breaking it.
- Environment management – Postman supports multiple environments so you can easily create different versions of the same API service and switch between them. This helps you define different test procedures and production data sets within the same collection, making it easy to ensure everything is working as expected before deploying updates.
- Documentation & sharing – Postman stores all of your documentation in a single place where you can access it from any device or location that has an internet connection. You can also publish collections anonymously so that your friends and colleagues can try out new features without having to sign up, or share them privately with an unlimited number of users.
- API mocking – You can test your APIs throughout the development process by creating mock servers for them using Postman’s mock server tool. This lets you check how they’re working before deploying updates onto your production server, which makes it ideal for testing against different data sets and scenarios.
OpenAPI Generator is an Open Source code generation tool that helps you create APIs from a Swagger/OpenAPI 2.0 or 3.0 definition and automatically update them as needed so you can keep all of your documentation and code in sync at all times.
- Code generator – OpenAPI Generator makes it simple to generate server stubs using the code generator, which you can then compile into your preferred language or framework. You can also use it to dynamically generate documentation based on your definitions for services that support OAuth2 and more complex authentication methods like tokens.
- Generator templates – There are currently over 100 generator templates available for languages such as C# (.Net Core), Java (for Spring Boot & Dropwizard), PHP (Lumen, Slim, Symfony), Python (Flask), and Ruby (Rails) that make it easy to create common API services.
- OpenAPI 3 support – OpenAPI Generator is fully compatible with all version 3 features like security schemes, response objects, input/output object, and more.
DapperDox is a free documentation generator for .Net Core and ASP.NET Core applications that helps you create clean API reference docs from Swagger or RAML files, including OpenAPI Specification (OAS) files.
- RAML support – DapperDox supports the open source library for easily generating API documentation from RAML definitions which can be hosted on GitHub pages. Once installed, it allows you to save your Swagger/OAS file as an HTML webpage complete with hyperlinks so users can navigate throughout your API using their browser.
- Markdown options – In addition to creating API documentation websites, DapperDox also provides a number of other formatting options that make it easy to generate Markdown (.md) files that can be used as a foundation for other documentation. This lets you quickly create API reference documents without having to install any additional tools on your computer.
Swagger UI is an interactive API documentation generator that renders your Swagger/OAS files in human- and machine-readable formats so your users can explore them without having to install any special software.
- Authentication & CORS – Swagger UI allows you to control both authentication and Cross Origin Resource Sharing (CORS) settings directly from the website interface, which means you don’t have to make changes to your code or create new pages to implement them.
- Templates & localization – There are several pre-configured templates included with Swagger UI that can easily be imported into an existing project, and it also supports localization so you can display all of the documentation in different languages.
API documentation tools can help you quickly create, manage, and distribute your APIs so they are easier to use. While some have limited capabilities, there are many open source options available that will work with any application or framework.