Disclosed is a system for composable chatbot extensions. Chatbot extensions are composed by providing the output of one extension as input to another. This defines a pipeline of extensions that accepts a prompt as input and provides a response as output. Composability makes it easier to leverage functionality provided by other extensions, log output, execute tasks in parallel, and test extensions. In some configurations, each extension declares the inputs it accepts, the outputs it produces, and any modifications it makes to data being passed through the pipeline. An extension may also declare a preferred location in the pipeline, enabling developers to choose whether to respond to a raw prompt as quickly as possible or to wait and receive intermediate results generated by other extensions. At the end of the pipeline a response is provided to the user via the chatbot.