Developers have consumed APIs as a matter of practice for some time now. It's second nature. But the flip side--creating an API--is not performed with the same regularity. To some extent, this is changing as more developers become both consumers and providers of APIs. Below you'll find some tools and services that make the process of creating an API much simpler.
Database to API
You already have a database, right? These two services and one standard can help expose that database as an API.
- Emergent One connects to MySQL and PostgreSQL databases and produces a RESTful API
- Espresso Logic creates an API from MySQL, then adds security and business logic
- OData is a standard (originally developed by Microsoft) and has libraries for most popular databases and servers
There are a growing number of services built to support mobile APIs. Any app that does anything interesting needs an API, but nothing says you need to use the API exclusively for mobile--or even have a mobile app at all.
- Parse is a popular app backend bought by Facebook
- StackMob touts a flexible and customizable backend
- Moblico, whose launch we covered in March (and who I have informally advised), focuses on common app features, such as loyalty programs
See also: over 100 backend-as-a-service APIs
Excel to API
Ever had data in CSV or Excel format, maybe from a client or a small personal project. You can move it to a database and then make an API, or use one of these services to cut out that database administration step. This is especially useful if a non-tech person needs to make frequent changes.
- Datownia allows anyone to create an API, we wrote almost a year ago. The company uses a mashup with cloud storage providers to maintain copies of the Excel document
- Socrata was originally a Platform for government data, but its business data launch boasted Excel Integration as a selling point
If you want to roll your own API, consider using a Framework for your programming language. For example, check out this list of PHP API frameworks. Or search for one in your favorite language. Heck, Ruby on Rails is known for an API "out of the box."
No matter how you create your API, the next thing you need to do is create Documentation. For more reading, consider the six pillars of complete developer documentation or an overview of automated API documentation.