Start a build and passing variables through Azure DevOps Rest API

Question

I would like to start a Azure Pipelines build through the REST API. There is an API for queuing builds but I couldn't find a way to define variables.

Answer 1

The accepted answer does not really answers the question when you need to set a value at queue time. The solution is actually pretty simple you just have to add a parameters field to the json payload. The content should be a json string (not directly an object) containing the parameters Ex :

{
    "parameters":  "{\"ReleaseNumber\":  \"1.0.50\", \"AnotherParameter\":  \"a value\"}",
    "definition":  {
                       "id":  2
                   }
}

EDIT : This feature is now properly documented as an optional stringified dictionary. See https://www.visualstudio.com/fr-fr/docs/integrate/api/build/builds#queue-a-build