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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the description doesn't need to repeat safety traits. The description adds valuable behavioral guidance: 'Return matches as evidence; never claim a part exists unless it appears in the result.' This is a critical anti-hallucination constraint that goes beyond annotations. It effectively communicates the tool is a read-only search and sets expectations for evidence-based responses.

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?

The description is three crisp sentences with zero fluff. The core verb and resource are front-loaded in the first sentence, the usage trigger is the second, and the evidence constraint is the third. Every sentence earns its place, and the structure is highly scannable for an agent.

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?

The tool has an output schema, so return-value explanation is unnecessary. The description covers purpose, usage triggers, and a critical behavioral constraint. The mention of 'public lens catalog' implies accessibility without special permissions. Given that siblings are clearly differentiated by resource type and the annotations carry safety information, the description is complete for an agent to call this tool correctly.

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%, meaning every parameter (query, limit, diameter_mm, wavelength_nm, focal_length_mm) has a description. The tool description does not add any parameter-specific guidance beyond the schema; it only refers to query being used for 'real lens part numbers' etc., which is already covered in the schema's query description. Baseline for high coverage is 3, and the description does not compensate with extra semantics, so 3 is appropriate.

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 a specific verb and resource: 'Search public lens catalog rows.' It also enumerates the user intents it serves (part numbers, links, focal lengths, diameters, coatings, purchasable candidates), and the resource name 'lens' clearly differentiates it from the fiber-focused siblings (search_fiber_collimators, search_fibers). No ambiguity about what it does or how it differs.

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?

The description explicitly says 'Use when the user asks for...' and lists the conditions, providing clear context for when to invoke the tool. It lacks explicit exclusions or mention of alternatives (e.g., 'use search_fiber_collimators for collimators'), but the sibling names themselves are self-explanatory and the usage context is unambiguous. A clear usage trigger without an explicit negative or alternative earns a 4.

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