Plans
This may begin with prose, and expand into something like a project plan at some point. This need not be a complete schedule, but it will make sense to include the steps and approaches, milestones, etc.
Dependencies
This should be a description of the major dependencies of the new service implementation. Example dependencies could be 3rd party utility classes, core classes or packages, other services, etc.
Test Plan
This should describe how the new service implementation will be tested. The testing here could include white box style test, unit test, and/or integration tests.