Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
The input schema already provides a description for the single parameter ('The idea ID'), and schema description coverage is 100%, so the baseline is 3. The description adds that the ideaId should be one 'you own', which is a useful constraint not in the schema. This justifies the baseline score.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.