Provided are a computer program product, system, and method for using higher order actions to annotate a syntax tree. An information space of the syntax tree is annotated with concepts corresponding to tokens in the syntax tree. A concept comprises an object in a domain of the question and relates to other concepts in an ontology of the domain. A higher order action specifies an input, action parameters, and an output. A determination is made of an element in the information space corresponding to the input of the higher order action. A determination is made of an action of in the domain of the question having parameters matching the action parameters. The determined element is input to the determined action to produce output. The information space of the syntax tree is annotated with the output from the higher order action to use to provide an answer to the question.