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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, non-destructive, closed-world), so the description only needs incremental value — and it supplies the return payload ('id, SKU, name and sku_url'), which matters because no output schema exists. It stops short of describing match-count behavior or how conflicting keys are resolved.

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 tight sentences with zero filler; the lookup modes are front-loaded before the return-value note. Every clause carries information the agent needs.

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 5-parameter lookup tool with no output schema, the description covers both the input keys and the returned fields, which is most of what an agent needs. It leaves minor gaps: no mention of the limit/pagination behavior for q, and no statement of what happens if multiple keys are supplied.

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 only 40% (q, id, sku, limit carry no descriptions), and the description compensates by mapping each lookup key to its semantics: sku=exact SKU, code=barcode, id=product id, q=fuzzy text search. That distinguishes exact-match keys from the fuzzy one, which the schema alone does not convey.

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 and resource ('Finds a product') and enumerates the four lookup modes with their parameter names, so the agent knows exactly what the tool retrieves. It does not differentiate itself from close siblings like search_products or get_products, which is the only thing keeping it from a 5.

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?

'Give one of them' is an explicit invocation constraint that tells the agent the lookup keys are mutually exclusive and one is required, even though the schema marks nothing as required. However, there is no when-to-use guidance against siblings such as search_products/get_products, so the routing decision is left to inference.

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