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

The description adds meaningful behavioral boundaries beyond the readOnlyHint annotation: it returns metadata only and never the paid depth/body content, and it notes the guide must be live. With annotations already covering the safety profile, this is solid additional transparency.

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?

One dense, front-loaded sentence that states the primary behavior, the returned fields, the limitation, and the valid input space without filler. 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?

For a simple one-parameter read-only tool with a full output schema, the description covers what the tool returns, what it never returns, and the valid slug set. Nothing an agent needs to invoke it correctly is missing.

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 coverage is 100%, but the description adds value by enumerating 19 known slugs (pregnancy, newborn, toddler, ...) and clarifying the slug must refer to a live guide. This is extra semantic guidance beyond the schema's example-based description.

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 ('Returns') with a specific resource ('one live guide's title, subtitle, access, book count, and reading time') and explicitly scopes it as 'card-level metadata only, never the paid depth/body content', which separates it from content-returning 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?

The description clearly defines when the tool applies — fetching metadata for a known live guide slug — but it does not explicitly name alternatives or state when not to use it. The sibling list helps infer boundaries, so the guidance is clear context, no exclusions.

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