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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered. The description adds valuable non-annotation context: output is short and plain-English, it is educational with no recommendation, and the no-argument behavior is a listing rather than a lookup.

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?

Three short sentences, front-loaded with what the tool returns, followed by the intended audience/limits and the no-parameter behavior. No filler and nothing repeated from the schema or annotations.

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 one-optional-parameter read tool with full annotation coverage and no output schema, the description covers scope, tone, and the omitted-argument case. Only minor gaps remain, such as whether a lesson is a single item or a multi-section response, which is largely implied by "short".

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% and the topic parameter already has examples, so baseline is 3. The description adds genuine meaning the schema lacks: omitting topic switches the tool into list mode rather than returning an error or a generic answer.

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?

States a specific verb+resource ("a short, plain-English lesson") with concrete example topics and a second scope ("how Unitrader handles it"). It implicitly separates itself from about_unitrader by being topic-level education rather than product overview, but no sibling is named.

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?

"Leave the topic out to list the lessons" gives an explicit conditional for the empty case, and "Education only, never a recommendation" sets the framing for when this is appropriate. It does not explicitly exclude the closest alternative (about_unitrader), so 4 rather than 5.

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