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

Annotations already cover safety (readOnlyHint, idempotentHint, openWorldHint=false, non-destructive), so the bar is lower. The description still adds real context beyond them: that results are limited to published plans and that the school/district option carries no numeric price because it is quoted per customer, which prevents an agent from treating a missing figure as an error.

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, front-loaded with the returned content, then the usage directive. Nothing is redundant with the title or restated for padding.

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 zero-required-parameter read tool with full schema coverage, an output schema, and rich annotations, the description covers purpose, trigger, and the one non-obvious edge case (per-customer school/district quoting). An agent has everything needed to call it and interpret the result.

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 single enum parameter already documents "Omit to get them all." The description never references the audience filter, so it adds no meaning beyond the schema — 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?

"Return every published Vooks subscription plan with its price, billing interval, audience and free-trial length" names a specific verb and resource and enumerates what comes back. The added clause about the school/district option being quoted per customer rather than priced distinguishes this from a generic pricing lookup and from the catalog-oriented siblings.

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?

"Use this to answer what Vooks costs instead of quoting a figure from memory" gives a clear triggering condition and explicitly steers the agent away from an incorrect alternative behavior (recalling a price). It stops short of naming a sibling tool it should be preferred over, but no sibling covers pricing, so the omission is minor.

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