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

Annotations already declare it as read-only, idempotent, and non-destructive, so the safety profile is covered. The description adds that it returns the API index with languages and HTML pages, which is useful content context, but it does not describe return format, size, or other behavioral traits.

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?

The description is a single front-loaded sentence with no wasted words. It is appropriately sized for a zero-parameter endpoint, though the phrasing could be slightly more precise.

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?

Given the low complexity and rich read-only annotations, the description covers the basic content of the endpoint. However, with no output schema, it leaves the exact return structure and how it relates to sibling discovery tools unspecified.

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 no parameter semantics to document. The schema is empty and fully covered; the description appropriately does not discuss parameters.

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 is a noun phrase that describes an API index containing languages and HTML pages, but 'index of the whole API' is vague and does not state an action or clearly distinguish it from sibling list_languages. It adds content beyond the title, but the purpose remains only partially clear.

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?

There is no guidance on when to use this tool versus alternatives. Sibling tools like list_languages and list_countries cover similar discovery needs, yet the description gives no context or exclusions.

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