I’d like to know whether a task must be self contained.
Our tasks mostly contain a couple of sentences.
To understand what you are to do you should:
- Read the requirements document for several related back log items.
- Know how system currently works and understand how it differs
from what is required.
In other words: newcomer or the person who was absent at the planning meeting will require a sufficient amount of time just to comprehend the task.
In addition such way of keeping backlog does not tell much about system evolution and looks more like a primitive contextually conditioned to-do list.
In most agile framework implementations, the tasks and stories are meant to be a reminder to have a conversation, not a fully detailed spec.
We have had similar problems where new team members who are not familiar with agile or who have missed the planning sessions struggle to work on their own without guidance. The simple solution here is to guide them.
Your Scrum Master, or whomever is playing a similar agile coach role, should be recognizing this dynamic in the team and should be making sure your team member knows that they can reach out to your Product Owner.
The Product Owner, or whomever is playing the role of owning the business requirements, should be available constantly to answer questions, refine acceptance criteria, and generally help the team understand what it is that needs to be built.
That being said, it is generally helpful to capture the output of discussions or decisions made during the conversation on your backlog tasks so that everybody remembers why a decision was made or why there was a deviation from the original criteria.