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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint, so safety and idempotence are covered. The description adds real value beyond them by flagging 'FREE' (no cost/quota) and by listing the returned fields, which matters because there is no output schema.

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?

One compact sentence prefixed by 'FREE.', with the capability front-loaded and the filter options trailing. No filler, and the cost signal appears first where an agent will see it.

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 three-param, zero-required lookup tool with no output schema, the description supplies the return fields, the filter axes, and the cost status. What's missing is only guidance on result limits or how the catalog relates to the purchase tools, a minor gap given its simplicity.

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 only 33% (toolset and max_price_usd are bare), yet the description accounts for all three: query as keyword, toolset as a filter, and max_price_usd as a price ceiling. It compensates for the thin schema, though it doesn't clarify accepted values or units beyond what max_price_usd's name implies.

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?

Specific verb (search) plus resource (products this server can buy) and an explicit enumeration of what comes back: ids, prices, parameters, and which tool sells them. That last detail cleanly separates it from siblings like call_product and get_price_quote, which act on a product rather than catalog it.

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?

It states the three filter axes (keyword, toolset, max price), which implies how to narrow a search, and 'which tool sells them' hints that call_product is the follow-up. But it never says when to reach for this instead of a sibling or when filtering is unnecessary, so the routing guidance stays implicit.

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