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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower, and the description still adds real context: 'Works without an API key' is an auth detail an agent needs before calling. It also frames the data as currently purchasable plans, implying live catalogue results rather than cached ones.

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 payload sentence is front-loaded with the resource and follows with the use_case guidance; nothing is filler. The long parenthetical enumeration of plan features makes it denser than necessary, but every clause conveys distinct information.

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 must convey return content, and it does: plan sizes, monthly USD prices, terms, and purchase instructions. What remains thin is whether responses are grouped per plan or how they should be presented, but nothing blocking an agent from calling it 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?

Schema description coverage is 100% and the enum values are individually explained in the schema, so the schema carries the detail. The description only adds a loose hint that use_case selects size and add-ons; it does not clarify value-specific behavior beyond that, so baseline 3 applies.

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 resource and scope: the plans a user can buy right now, enumerating the Commercial API sizes and the app plans (Pro, Dealer, Enterprise) with prices in USD. This clearly separates it from get_card_prices (per-card pricing data) and start_checkout (transaction), so an agent can pick it without opening the 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 a concrete routing rule: 'Pass use_case to get the size and add-ons that fit what the user wants to do,' which tells the agent when the parameter is worth setting. It lacks explicit when-not-to-use guidance or named alternatives to get_card_prices/start_checkout, but the usage context is clear.

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