A key challenge for mixed-initiative systems is to create a shared understanding of the task between human and agent. To address this challenge, we created a mixed-initiative interface called Mixer to aid administrators with automating tedious information-retrieval tasks. Users initiate communication with the agent by constructing a form, creating a structure to hold the information they require and to show context in order to interpret this information. They then populate the form with the desired results, demonstrating to the agent the steps required to retrieve the information. This method of form creation explicitly defines the shared understanding between human and agent. An evaluation of the interface shows that administrators can effectively create forms to communicate with the agent, that they are likely to accept this technology in their work environment, and that the agent's help can significantly reduce the time they spend on repeated informationretrieval tasks. Author...