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

Annotations carry readOnlyHint and openWorldHint, but the description adds valuable behavioral detail: comparisons[] is written from product_id's point of view, products without a stored comparison have none, and buying-guide text is Romanian for language=ro and English otherwise. This goes well beyond what annotations and the schema alone convey.

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 dense but every clause earns its place: core capability, use cases, alternative mode, sibling differentiation, comparison directionality, and language behavior. It is longer than ideal, but the content is high-signal and front-loaded with the primary action and scope.

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 3-parameter read-only tool with no output schema, the description covers the essential context: parameter cardinality constraints, alternative mode semantics, comparison directionality, missing-comparison behavior, language behavior, and how it differs from get_product. An agent has enough to select and invoke 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?

The schema already documents all parameters with 100% coverage, so the baseline is 3. The description adds meaning by explaining the relationship between product_ids and with_alternatives, the 2-to-4 vs exactly-1 constraint, and the language-dependent behavior of the buying-guide text, which the schema only partially hints at.

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 names a specific verb and resource ('Compare 2 to 4 products side by side') and details the exact kinds of data compared: price, stock, specs, and suitability. It also distinguishes itself from get_product by explicitly noting where the full description and accessories live, so an agent can tell the tools apart.

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 gives concrete example questions the tool is good for ('X or Y?', 'what is the difference between...'), states the alternative-mode requirement (one product_id with with_alternatives=true), and names get_product as the tool that has the full description and accessories. This is explicit when-to-use guidance with an alternative.

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