Software developers want a way to integrate their software with theirs, and they don't want things to break down for them. This is where an API comes in.

It is the nature of software development. Developers create software with the end user in mind. It sounds simple enough, but sometimes those users are fellow developers too. They don't need things to be broken down for them. They don't even need the simplicity. All they want is access, a way to integrate your software with theirs. This is where an API (application programming interface) comes into play.

The five steps to creating a successful API are:

1. Do your homework

When it comes to software development, none of us want to reinvent the wheel. At this point, almost all large web companies have APIs for their software products. Study these APIs and try to capture the different design decisions that were made to create them.

2. Be consistent

One of the things developers appreciate the most is consistency. This includes, but is not limited to, addressability, input arguments, output formats, and error handling.

When using a RESTful approach, there are many different URI naming schemes. Each one has its followers, so just pick one and stick with it. The same goes for the input and output structure. Most APIs support the use of XML and JSON as input and output formats. I would suggest supporting both, but choosing a default format.

For input, your input requirements must be named consistently and must make sense in the context of the API call you are making. For the output, make sure you are using common data structure layouts. If you wrap the result of an API call in an XML tag, consider doing it with your other calls.

It is common practice to include some type of status indicator in the output data that you send to the client. When using a RESTful API approach, this must be done using HTTP status codes. For example, if you just processed a PUT request on an existing data object, the HTTP status code that you include in your response will vary depending on the result of the request.

Instead of an arbitrary flag indicating the status of the call, a standard "200 OK" status code can be used to indicate that the request was successful, while a "400 Bad Request" status code could be used to indicate that the application was malformed. There are quite a few HTTP status codes that can be used in different situations.

3. Use OAuth

Most software products involve some type of user authentication to access the protected resources for that user. When it comes to APIs, having the client collect user credentials to send to your server is bad practice. This is where OAuth comes in.

OAuth offers many benefits over third-party username / password authentication. Above all, the client never has access to the user's credentials. The user is redirected to your server when they log in. Once the user logs in to your site, they are redirected back to the client, where the client will receive an access token to use for future requests for protected resources.

Another important benefit of using OAuth is the ability for the user to cancel client access at any time. If the user decides that, for whatever reason, they no longer want the client to be able to access the protected resources on their behalf, they simply go to an interface that they have created and cancel the client's access.

4. Start early

One of the most important things you can do to make your API a success is to start early. When you write that function to create some entry in your database, go ahead and take the extra time and write an API interface for it. https://www.restcase.com/

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Another important benefit of using OAuth is the ability for the user to cancel client access at any time. If the user decides that, for whatever reason, they no longer want the client to be able to access the protected resources on their behalf, they simply go to an interface that they have created and cancel the client's access.