Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, so baseline is 3. The description adds value by explaining the parameter's purpose in context: 'pass an ideaId you own' clarifies the parameter must be an idea owned by the user, which is not explicit in the schema's minimal 'The idea ID' description. This extra context raises the score.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.