Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 0%, so the description carries the burden and does explain all three parameters: q is a text filter, tag matches a rolodex tag, mine=true restricts to the user's own projects. It leaves q's matching semantics (substring vs. full-text) and tag format unstated, so not a 5.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.