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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety bar is pre-cleared. The description adds real value beyond that: it enumerates the returned payload (all plan options with price per 1000, min/max quantity, quality tier, typed axes, delivery speed, recommended flag) and notes the conditional availability of the x402 and checkout flows. It stops short of pagination or size/rate limits, so not a 5.

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?

Front-loaded with the core action and the two alternatives, then the return payload, then downstream routing. Every sentence carries information, though the parenthetical conditionals about which endpoints are 'listed' make the tail dense and slightly harder to scan than necessary.

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?

With no output schema, the description fully compensates by detailing exactly what is returned (plan-level fields and the recommended flag) and how to use the result downstream. An agent has everything needed to call this correctly and interpret the response.

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?

Only one parameter and schema description coverage is 100%, so the schema already defines service_id and its origin ('from search_catalog'). The description reinforces this ('you already have the id for') but adds no format, validation, or edge-case detail beyond the schema, matching the baseline 3 for a fully covered schema.

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 ('Look up ONE service') and immediately scopes it to a known id. It explicitly differentiates itself from search_catalog (when no id exists) and recommend_service (when a single option is wanted), so an agent can pick it without opening a schema.

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?

Gives explicit when-to-use routing ('No id yet? Find one with search_catalog', 'Want a single option...? Use recommend_service') and names the downstream consumers of the returned service_option_id (get_quote, create_paid_order, create_checkout). Nothing about selection 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.