Microsoft REST API Guidelines
Every single person writing a REST api should have to memorize this table:<p>GET - Return the current value of an object, is idempotent;<p>PUT - Replace an object, or create a named object, when applicable, is idempotent;<p>DELETE - Delete an object, is idempotent;<p>POST - Create a new object based on the data provided, or submit a command, NOT idempotent;<p>HEAD - Return metadata of an object for a GET response. Resources that support the GET method MAY support the HEAD method as well, is idempotent;<p>PATCH - Apply a partial update to an object, NOT idempotent;<p>OPTIONS - Get information about a request, is idempotent.<p>Most importantly, that PUT is idempotent.<p>Credit to arkadiytehgraet for retyping the table to be readable.  Please give them an upvote for the effort.