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

Annotations already declare readOnlyHint, idempotentHint, and a closed-world scope, so safety is covered. The description adds real behavioral context beyond that: a hard cap of 5 results, the provenance (Cambridge examiner reports), and the shape of each item (short summary plus a link).

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 with the result cap and provenance front-loaded, followed by the narrowing advice. The only blemish is the odd 'exam.now' token, which reads like a stray artifact and slightly blunts an otherwise clean statement.

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 small read-only lookup tool with no output schema, the description covers the essentials: bounded result count, source, per-item structure, and how to filter. It lacks detail on what happens when no mistakes match, but nothing critical to correct invocation is missing.

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%, with all three parameters documented with examples (query 'bounds', topic 'E1.10', subject codes like 0580). The description only restates the topic/query narrowing at a high level, adding nothing the schema does not already carry.

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 gives a specific verb-and-resource pair: retrieving up to 5 examiner-report write-ups of common mistakes for a subject. That is clearly distinct from siblings like find_questions_by_topic or get_mark_scheme, though it never explicitly contrasts itself with them.

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?

It tells the agent how to narrow results (topic code or words), which is useful operational guidance. It does not say when this tool is preferable to find_questions_by_topic or topic_progress, nor when not to use it.

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