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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds valuable context not in the annotations or schema: the result is a set of passages, each tagged with the lesson it came from. It doesn't mention result size or behavior for unknown terms, which keeps it below a 5.

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 sentence that front-loads what the tool returns and uses the parenthetical only for illustrative terms. Slightly dense colon construction but no wasted sentences.

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-parameter read tool with rich annotations, the description covers purpose and return shape (passages plus provenance) despite there being no output schema. Only edge-case behavior (no matches found, ambiguous terms) is left unaddressed.

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%, so the baseline is 3. The description improves on the schema's terse 'one or a few words' by giving concrete example terms, which clarifies acceptable granularity (single words or short phrases like 'crown angle').

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: it reports what the lessons say about a single gemology term and what it returns (passages with their source lesson). Concrete example terms ('table', 'crown angle') pin down scope. It doesn't explicitly contrast with search_lessons, so sibling differentiation is left implicit.

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 phrasing 'what the lessons say about one term' – an agent can infer this is for term-definition lookups rather than listing or fetching lessons. But there is no explicit when-to-use, when-not-to-use, or named alternative such as search_lessons.

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