Buckets use Markdown formatting, a simple type of formatting that works through html. It might sound a little scary, but it's very easy to use!
When creating a bucket, you are free to add anything you like in the description! To make your bucket as clear and convincing as possible, here are some suggestions on what you could include:
Context: why this idea?
Deliverables: what will be the concrete outcome of the project?
Breakdown of costs: show what people's funds will go to in more detail
Who is going to do the work? (If not just you)
Timeline: what deadlines and milestones are there for the project?
Link to more details: using markdown formatting, you can add external links. Add a link to a document or external website describing your idea in more detail, to be able to keep your bucket concise, yet give more details to those who want them.