1. A method executed on a computing device for providing document communication runtime interfaces, the method comprising: facilitating document-centric messaging for transmitting calls supporting a script object model; providing security employing at least one of a policy checking mechanism over the messaging, wherein a receiving entity confirms whether a transmitting entity is allowed to transmit a call, and a sandbox process to manage extension content traffic between an application hosting a document and third party web services providing the extension content; providing a solution manager to determine which extensions relate to an instance of the application, a document content type, and document content, and to obtain configuration and policy information from manifest files cached on a user machine; monitoring aspects of the extensions; and one of stopping and restarting the extensions based on violations of predefined metrics.