Purpose:

• Make the case for the addition
• Describe the shape of the solution
• Identify potential challenges

Entrance criteria:

• Identified “champion” who will advance the addition
• Prose outlining the problem or need and the general shape of a solution
• Illustrative examples of usage
• High-level API
• Discussion of key algorithms, abstractions and semantics
• Identification of potential “cross-cutting” concerns and implementation challenges/complexity
• A publicly available repository for the proposal that captures the above requirements

See https://tc39.es/process-document/