Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so the description's extra value is in disclosing output shape, the graceful "says so when evidence is limited" behavior, and a cost signal. These are genuinely useful beyond the annotations, though "moderate cost" is vague with no unit or threshold.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with the purpose, then the return contents, then behavioral caveats and scoping advice. Dense but every clause earns its place; no filler or repetition of the title.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists, so the description needn't enumerate return values, yet it does so helpfully, and it adds the degradation behavior and cost note. What remains thin is the relationship to the other insight tools, which matters given three near-siblings in the toolset.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100% with clear per-parameter docs (days=0 means school year, classId from list_classes, etc.), so the schema carries the burden. The description only reinforces subject scoping, adding little beyond what the schema already provides — baseline 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description names a specific verb+resource (class progress on AP course skills) and enumerates the outputs — per-skill verdict, average, trend, at-risk students, units to revisit — so the agent knows exactly what it returns. It differentiates implicitly by granularity from get_class_insights and get_student_insights, but never names those siblings to make the distinction explicit.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

"Works best scoped to one subject" and "Moderate cost" give practical usage guidance, but there is no statement of when to prefer this over get_class_insights, get_student_insights, or get_reteach_gaps, and no when-not conditions. The agent is left to infer the routing.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.