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 contributes the useful fact that the result spans two categories (caption input languages vs. translation targets), but says nothing about whether the list is static, how it's structured, or how large it is.

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 two categories are front-loaded. The phrasing ('The spoken languages... and the languages it...') is slightly convoluted but still readable and earns its space.

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 no-param, read-only lookup with no output schema, the description conveys the essential shape of the response (two language groupings). It stops short of describing the return format or ordering, but that is a minor gap for such a simple tool.

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 nothing for the description to disambiguate; baseline 4 applies. No parameter text is needed here.

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 names a specific resource (spoken languages for captioning and translation targets) and effectively answers 'what does this return.' It doesn't use an explicit verb like 'list,' but the intent is unambiguous and clearly distinct from sibling tools like get_pricing or get_faq.

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?

Usage is only implied: an agent can infer it should call this when it needs to know supported caption/translation languages. No explicit when-to-use, when-not-to-use, or alternatives are stated, though the sibling set makes conflicts unlikely.

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