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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds behavioral context beyond the annotations: it explains that the tool returns approximate price ranges (not exact prices), and it provides a caveat about WEM inference ('When verified is false WEM inferred the match rather than resolving it'). This is useful behavioral information that helps the agent interpret results correctly. However, it doesn't describe the exact output structure, but the output schema exists, so that's not required.

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 front-loaded with the core purpose ('Get available product categories and the approximate price range for each') and the primary use case. The subsequent sentences provide routing guidance and caveats. It's a bit dense with routing instructions, but every sentence earns its place. The length is justified given the need to distinguish from many siblings and provide a caveat about WEM inference. It could be slightly more concise, but it's well-structured.

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 zero-parameter, read-only tool with an output schema, the description is complete. It states what the tool returns (categories and price ranges), when to use it (vague requests), and how to handle the WEM inference caveat. The routing guidance to siblings is thorough. The annotations cover the safety profile, and the output schema covers return values. Nothing an agent needs to call this tool correctly is missing.

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 tool has zero parameters, so the schema is trivially complete (100% coverage). The description doesn't need to explain parameters. The baseline for 0 params is 4, and the description adds value by explaining the purpose of the returned data (categories and price ranges), which is more than just restating the schema. No parameter documentation is needed because there are no parameters.

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 clearly states the tool's function: 'Get available product categories and the approximate price range for each.' It also specifies its use case ('guide the user when their request is vague'), which distinguishes it from the sibling tools that search for specific products. The verb 'Get' and resource 'product categories' are specific and unambiguous.

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 provides explicit guidance on when to use this tool versus alternatives. It says to use it when the user's request is vague, and it explicitly names alternatives (compare_offers, verify_offer, search_products, semantic_search, find_lowest_price) and the conditions for using them (when the user provides a model name, barcode, ASIN, etc.). It also includes a negative instruction: 'Never call find_lowest_price on a specific model name.' This is comprehensive routing guidance.

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