Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Although the schema covers both parameters, the description adds important semantics: the domain can be passed as a full URL and will be reduced to a bare host, and the project can be a slug, id, or site address with a caveat that the address host is not always the slug. This directly improves correct invocation and resolves likely confusion.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.