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

Annotations already declare this a read-only, idempotent, non-destructive operation, so the description earns credit for going beyond that. It discloses two behavioral traits that matter for interpretation: results are anonymised (no pupil names) and small groups are suppressed for privacy, meaning counts and bands may be withheld or incomplete. It does not explain the suppression threshold or what 'started' means, which keeps it below 5.

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?

Two tight sentences, front-loaded with scope and immediately followed by the privacy caveat. The opening is a sentence fragment ('For a teacher's own exam.now class: ...'), which is slightly awkward but not wasteful; no sentence is redundant.

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?

For a simple read-only aggregation tool with full schema coverage and no output schema, the description adequately sketches the return shape (topic bands, count of pupils started) and flags the privacy suppression that would otherwise surprise an agent. Minor gaps around grouping granularity and thresholds remain, but nothing essential is missing for correct invocation.

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 coverage is 100%, so both parameters are already documented, including the hint that omitting class_id targets the teacher's own class. The description reinforces the 'own class' default but adds no new syntax, format, or edge-case detail. Baseline 3 is appropriate when the schema carries the parameter burden.

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 the resource precisely: class-level topic bands plus a count of pupils who have started, scoped to the teacher's own exam.now class. That is specific enough to separate it from per-pupil siblings like topic_progress or common_mistakes. It stops short of naming an alternative outright, so it is a strong 4 rather than a 5.

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?

Usage is only implied through the phrase 'For a teacher's own exam.now class', which signals the audience and default scope but not the conditions under which an agent should pick this over topic_progress or common_mistakes. There are no explicit when-not-to-use statements or named alternatives.

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