10 tips on how to build the perfect SDK

This post was born as a query of a friend of mine who thought there was not enough documentation on writing a good SDK that others can easily use.

In the last decade, SDK usage has become a major part of the development lifecycle. In fact it is so commonly used and integrated into products, that one would say developers need to acquire more knowledge with many frameworks rather than learning deep algorithms to implement by themselves.

This post is mainly addressed those who want to learn how to write the best SDK and supply documentation for it.

The goal/orientation of an SDK is that its documentation should be focused and clear.

If you feel there is more than one focus area - consider splitting it.

Below is a list which I hope would help you construct an SDK in a good way and writing its documentation:

0.     Learn what is out there

Try to see what your competitors or companies in similar domain as yours have done.

This may give you a point of reference. Take what you like and improve what you did not like.

1.     Simplicity

Code - simple code means your consumers find it easy to use. This might include as few as possible way to interact with your code, e.g. expose only one interface class; short method signatures, e.g. small number of input parameters; etc.

Except of initiation, which occurs once and might require some configuration, make the usage of your SDK methods as simple as possible.

As such -  try to keep method signature with as few parameters as possible.

You can achieve this by providing default configuration and default implementation classes, that can be overridden by advanced users.

Hide any class and method consumers don't need to use, i.e. make classes/methods public only if consumers must use them, otherwise use local or private scope. Some IDEs can help you do it automatically via code inspection and cleanup.

Documentation: Make your documentation as simple as possible. This means sometimes to write more explanatory text and sometimes write as less as possible. Inline code samples often help, as most humans learn by example.

2.     Provide an easy start - the way someone can use your code in less than 5 minutes. This is important as consumers want as little integration effort as possible, moreover, sometimes consumers want to evaluate your product, and without an ability to easily experiment with it, they would probably choose to skip it.

3.     Keep it short

This section is mainly relevant for documentation, but is also related to the ways the consumers can interact with the SDK code. In regards to documentation; this can be achieved by providing code samples and self-explanatory method names and using defaults.

4.     Integration - keep in mind the diversity of your consumers development environments.

For example, If you are writing an android library, the integration with it vary if your consumers user Android Studio with gradle (that requires aar artifacts and publishing to a remote repository) or they use Eclipse where you need to provide jar files, instruction about how to change the AndroidManifest.xml and a standalone eclipse project for the SDK.

This would impact your build mechanism & it's artifacts. However, don't try to win it all from day one. Do what fit most to your first client or to most of your predicted consumers.

5.     Sample project

Create the most basic project in GitHub that simulates a client that uses your SDK.

This would demonstrate your consumers how your product can fit their needs as well the easiest way to integrate with your product.  If you want to show an advanced usage, do it in another project. Often your consumers would use it as their main source of documentation, so provide inline comments and write code in a self-explanatory way as possible.

6.     Overview - in the beginning of the documentation or in the README.md file in the GitHub project, provide an overview about your solution in plain English. In this section, I usually like to provide a sample use case that will explain a typical SDK usage. If possible, provide a simple diagram or chart so people that don't like to read manuals, will see the benefit of your SDK quickly.

7.     Initiation - use conventions that are acceptable in the SDK domain.

It may be constructors with overload, build pattern or similar. The initiation should smartly use defaults in order to keep easy start.

8.     Defaults 

Defaults are important to keep code simplicity and reduce configuration (see the simplicity section). The defaults you provide (either configuration or implementation) shall represent the way you think most of the consumers will use your SDK.

You can provide several method overloading, where the simplest signature would call the more advance method signature with the default.

9. Publishing

• Offline use non-editable format - PDF. The advantage is that you can easily create one, store it locally in Dropbox and for each update, the version is updated automatically.
• Online - your corporate website. This is the preferred way, however, it might create a hassle of some IT overhead when you update it.

Hope those guildelines helps. Feedback is more than welcome.

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