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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely useful context that no structured field carries: what each feature record contains (summary, cheapest plan including it, credit cost, page URL), which compensates for the absent output schema. It stops short of any pagination, result-count, or ordering behavior.

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 core payload described first and the optional filter last. Every clause 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?

One optional, fully documented parameter; rich safety annotations; no output schema, so the description correctly absorbs the return-value description. An agent has everything needed to call it correctly.

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 fully listed in the schema, so the baseline is 3. The description's 'only the features available on a given plan' restates the schema's own wording and adds no format or edge-case detail (e.g., what happens for a plan with no features).

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+resource ('list features') and enumerates the returned payload (one-line summary, cheapest plan, credit cost, page URL), which makes it recognizable next to siblings like get_pricing. It does not explicitly differentiate itself from any sibling or state what problem it solves for the agent, so it falls short of a 5.

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 only usage signal is 'Optionally only the features available on a given plan,' which is really parameter behavior, not tool-selection guidance. There is no statement of when to call this versus get_pricing, get_brand_facts, or ask_question, and no prerequisites or exclusions.

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