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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds nothing beyond that: no note on what happens with an invalid or missing id, no indication of auth requirements beyond the schema, and no sense of payload size.

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 short fragment with zero filler, front-loading the resource and its identifier. It is efficient, though its extreme terseness borders on under-specification rather than deliberate concision.

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 single-record getter with full schema coverage and annotations covering the safety profile, the definition is minimally adequate. It still omits what the lesson payload contains and how failures are surfaced, which an agent calling it blind would want to know.

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%, with lesson_id documented as 'ln_...' and api_key explaining the alternate auth channels. The description merely repeats the 'ln_...' format hint already present in the schema, adding no new meaning, so the baseline 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 phrase 'One lesson by id (ln_...)' names the resource and the identifier format, implying single-item retrieval, but never uses an explicit verb like 'fetch' or 'retrieve'. It does implicitly contrast with search_lessons by scoping to a single id, but only weakly.

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?

No when-to-use guidance and no mention of alternatives, even though search_lessons is a direct sibling for the case where the id is unknown. The agent must infer that this tool is only for known ids.

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