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

Annotations already declare readOnlyHint, idempotentHint, non-destructive, and closed-world, so the safety profile is fully covered. The description contributes the substantive fact that the data spans two distinct language sets (input and translation targets), which is beyond what the annotations say. It does not describe the response shape or whether the catalog is static.

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?

A single sentence with no filler, and the key substance is front-loaded. It reads as a noun phrase rather than a clause ('Returns the spoken languages...'), which slightly weakens the opening but wastes no words.

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-parameter lookup with no output schema, the description should ideally characterize what comes back — e.g. two lists, whether codes or display names are included. It signals the two categories but not the structure, leaving a meaningful gap for an agent that must consume 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?

The tool takes zero parameters, so the schema baseline of 4 applies. No parameter meaning needs to be conveyed, and the description correctly does not invent any.

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 identifies the resource precisely and adds a useful distinction: it returns both the spoken languages accepted as caption input and the languages captions can be translated into. It lacks an explicit verb such as 'returns/lists', but the scope is unambiguous and sibling tools (get_faq, get_pricing, etc.) do not overlap.

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 explicit when-to-use statement, no mention of alternatives, and no prerequisites. Usage is nonetheless strongly implied: an agent needing supported caption/translation languages would call this. Implied rather than stated guidance.

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