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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds useful behavioral context: it enumerates what is returned (plan, dates, remaining quota/limit per allowance) and the 'call it once' guidance implies a stable, cacheable, side-effect-free read. It stops short of stating auth requirements, but nothing contradicts the annotations.

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 sentences, zero filler, with the primary purpose front-loaded and the routing guidance second. Each sentence earns its place.

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 must sketch the return value on its own, and it does: plan identity, plan dates, and remaining quota/limit per allowance. For a zero-parameter, non-destructive read that is sufficient, though it could say slightly more about what 'each quota and limit' comprises.

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 the baseline is 4 and there is no parameter syntax the description needs to compensate for. No param-level value could be added here.

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 ('Shows the caller's plan, its dates and how much of each quota and limit is left') and implicitly distinguishes itself from the many list_* siblings by naming them as alternatives for item-level data. An agent can identify this as the plan/quota probe 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 ('Call it once before you say which plan includes a reading') and when-not/alternatives ('Use list_views, list_watchlist or list_destinations for the items behind a count'), naming three concrete sibling tools. Nothing 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.