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

readOnlyHint=true already establishes it as a safe read, and the description usefully adds the shape of what comes back (seat limit, billing mode, price in the smallest currency unit). No pagination or caching behavior is stated, but for a static catalog-style listing the disclosure is solid.

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?

Two short sentences, with the content of the listing front-loaded before the audience/use case. No filler or restatement of the tool name, though the opening reads slightly like a data label rather than an action.

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?

There is no output schema, so the description carries the return-value burden and does so by enumerating the key fields. Combined with readOnlyHint and zero parameters, an agent has enough to call it correctly; only currency/formatting nuances remain unstated.

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 takes zero parameters, so there is nothing for the description to disambiguate; baseline 4 applies. The parenthetical note that prices are in the smallest currency unit is a helpful data-semantics hint even though it concerns output rather than inputs.

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 names the resource (gym subscription tiers on offer) and enumerates its contents (seat limit, billing mode, price per currency), so the agent knows exactly what this returns. It does not explicitly distinguish itself from siblings like list_organization_plans or list_subscriptions, but the purpose is 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 clause 'For a gym deciding what to buy or upgrade to' gives a real usage context, which is more than nothing. However, it names no alternatives and gives no exclusions, leaving the agent to infer when to pick this over the other organization/subscription listing tools.

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