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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered structurally. The description adds genuinely useful behavior beyond that: the result is a link to an external test on the site, and the agent must not attempt to administer the test inside the chat. It doesn't discuss link expiry, session persistence, or what happens on repeated calls.

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 sentences, zero filler. The usage trigger leads, the return value follows, and the prohibition against running the test in chat closes it — everything is front-loaded and each clause carries information.

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?

With one optional parameter, full schema coverage, and an output schema handling return structure, the description covers everything an agent needs to decide and call. The only missing piece is guidance on what to tell the student to do with the returned link (e.g., that they should open it themselves), which would round it out.

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%, and the single enum parameter already documents 'Omit when they are not sure which exam to take' as well as giving the 'pte' example. The description's mention of omitting the exam duplicates schema content rather than extending it, so the baseline of 3 applies.

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 states two concrete scenarios — no exam chosen (diagnostic) vs. exam known but wanting a baseline (placement) — and clarifies the output is a free test link on the site rather than an in-chat test. This differentiates it from siblings like practice_question or score_writing, though the differentiation is implied by the return behavior rather than named explicitly.

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?

Clear trigger conditions are given for both modes (student unsure of exam, or ready for a baseline placement), plus an explicit when-not: 'do not try to run the test in chat.' It doesn't name any sibling tool as an alternative, so it falls short of the top band, but the routing conditions are unambiguous.

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