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

Annotations already establish read-only, idempotent, non-destructive, closed-world behavior. The description adds useful context beyond annotations: it requires an api_key issued in the admin panel and enumerates the returned fields even though no output schema exists. It does not discuss rate limits or pagination details.

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 two tightly written sentences: the first front-loads the returned plan details, and the second gives the usage comparison and auth requirement. Every clause adds distinct information, with no filler.

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 low-complexity read-only list tool with rich annotations and a fully described single parameter, the description is complete enough. It enumerates return fields in lieu of an output schema, states the auth requirement, and routes the agent to get_usage for comparison.

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%, so the api_key parameter is already documented as a string with an sk_live_ example. The description adds provenance beyond the schema by noting the key must be issued in the admin panel, which is useful but limited given only one parameter.

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 states a specific return resource and enumerates exactly what is returned: monthly price, included minutes, concurrent sessions, max session length, avatar count, and overage price per plan. It also names the sibling tool get_usage for comparison, making the resource and scope distinguishable.

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 explicitly tells the agent to compare with get_usage usage when choosing a plan, giving clear usage context. It does not state when not to use list_plans or cover other alternatives, so it falls short of the top score.

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