What artifact should be attached to a task to start development?

The key artifact for starting development is the technical specification (TS) or requirements specification. It should clearly describe:

• Goals and objectives of the development
• Functional requirements
• Non-functional requirements (performance, security, etc.)
• Acceptance criteria
• Constraints and assumptions

Without such a document, developers will not be able to unambiguously understand what needs to be implemented.

In some teams, they additionally attach:

• Mockups or interface prototypes
• Business process diagrams
• User stories or usage scenarios

An example of a simple task template with an attached TS:

Task: Implement user registration form

Attached artifact: Technical specification "User Registration v1.0"

Description: The TS describes form fields, validation, error handling, and server interaction.