Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, so the structured data already fully documents id, slug, and language. The description adds the phrase 'by stable id or slug,' which is redundant rather than new meaning. With the schema already carrying the parameter details, the baseline of 3 is appropriate.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.