List languages

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds two genuine behavioral facts beyond that: results are scoped to this API key's plan, and they are time-sensitive ('right now'), which signals the agent should not cache them. It says nothing about the return shape or ordering, though the phrase 'language codes' does at least indicate the value type.

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 short sentence with no filler, and the most decision-relevant qualifier ('right now') is placed before the qualifier about plan scoping. It is a fragment rather than a full clause, but nothing in it is wasted.

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, read-only listing tool with no output schema, the description covers what is returned and why results might vary. The main thing left unstated is the code format (e.g. BCP-47/ISO), which an agent would need to match against a target-language argument.

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 carries no semantic burden and there is nothing for the description to compensate for. The baseline of 4 applies; the description's plan-scoping note arguably adds a small amount here since it explains why no filtering parameter exists.

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 — the language codes available for dubbing — and narrows it by plan and current availability. It is a noun phrase rather than a verb-led statement, and it does not explicitly contrast itself with siblings such as list_dubs, but the subject matter is distinct enough that an agent can identify it immediately.

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 when-to-use guidance and no mention of an alternative. The phrase 'can dub into right now' faintly implies this is a pre-check before requesting a dub, but the agent must infer that relationship to dub_media on its own.

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