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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is fully covered. The description adds value beyond that by disclosing the return payload shape (component, date, AM/PM session, duration, plus a timetable link) and the zone default, which matters because there is no output schema.

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?

A single dense sentence that front-loads the resource and scope before the field list, with no filler. It is slightly list-heavy but every clause carries information an agent needs.

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 three-parameter read-only lookup with no output schema, the description covers purpose, defaults, series options and returned fields. It stops short of stating error behavior for unknown syllabus codes or whether results are authoritative, which are minor omissions at this complexity level.

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 only 33%, so the description carries extra burden. It does clarify that subject_codes accepts one or more syllabuses and that series is June or November 2026, and it explains zone functionally as the UK timetable default; however it never explains what zones 1-6 represent or what the 10-code cap means in practice.

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 specific resource (Cambridge exam dates), the scope (one or more syllabuses), and the two series it covers, then enumerates the returned fields: component, date, session and duration. No sibling tool deals with timetables, so there is no ambiguity about which tool to pick for this need.

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 implied by the scope statement rather than stated: an agent can infer it should call this when it needs exam dates for specific syllabuses. There are no explicit when-to-use/when-not rules and no alternatives named, though none of the siblings overlap, which limits the practical cost of that gap.

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