A development platform for developing a skill for a persistent companion device (PCD) includes an asset development library having an application programming interface (API) configured to enable a developer to at least one of find, create, edit and access one or more content assets utilizable for creating a skill, an expression tool suite having one or more APIs via which are received one or more expressions associated with the skill as specified by the developer wherein the skill is executable by the PCD in response to at least one defined input, a behavior editor for specifying one or more behavioral sequences of the PCD for the skill and a skill deployment facility having an API for deploying the skill to an execution engine of the PCD.