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

The description discloses a critical behavioral trait beyond annotations: actual cue text is BotGuard-gated keyless, and the tool reports 'available:false' or empty segments rather than fabricating data. This adds important context about reliability and honesty, exceeding what readOnlyHint and idempotentHint already convey.

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 two sentences, front-loaded with the core purpose, followed by usage and a concise limitation note. Every word earns its place, with no redundancy or extraneous information.

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 only three optional parameters and no output schema, the description adequately explains what the tool returns (caption-language list and cue segments where retrievable) and how it behaves when not retrievable (available:false, empty segments). This covers the essential information for correct selection and use.

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% with descriptions for all three parameters. The description's 'Provide url OR videoId' adds exclusivity that is also already stated in the schema's parameter descriptions, so it does not significantly enhance parameter understanding beyond the schema.

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 clearly states the tool returns available caption-language list and cue segments for a YouTube video, specifying the resource (YouTube video) and scope (caption languages). It is distinct from sibling tools, which are all social media related, so there is no ambiguity about what this tool does.

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 provides explicit usage instruction 'Provide url OR videoId' and notes the keyless access, giving clear context on how to invoke it. It does not explicitly mention alternatives, but the sibling tools are unrelated (social media), so the intended use case is implied and unambiguous.

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