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

No annotations are provided, so the description carries the full burden and does so well: it discloses the return shape (title, channel, language, auto-generated flag, language-fallback flag, text and segments), per-call limits, the fallback-to-original-language behavior, and the error contract (status 'error' with a code and retryable flag for missing captions or blocked videos).

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?

Front-loaded with the core action and resource, then usage guidance, then the return/error contract. Dense and information-rich with no filler, though the long compound sentences make it heavier than strictly necessary.

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?

Even without an output schema, the description documents the result fields, the language-fallback semantics, and the error shape, which is everything an agent needs to call it and interpret the response correctly for a read-only retrieval 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?

Schema description coverage is 100%, so the schema already documents all five parameters, and the baseline is 3. The description only restates the parameter surface ('plain text, timestamped segments, SRT or VTT, optionally in a chosen or translated language') without adding format or syntax detail 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?

States a specific verb and resource ('Fetch the full transcript of a YouTube video URL or ID') plus the output formats (plain text, timestamped segments, SRT, VTT) and the optional language/translation dimension. An agent immediately knows this is a YouTube caption-retrieval tool and what it yields, with no ambiguity against the unrelated sibling tools.

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?

Explicitly says when to use it ('when the user asks to summarize, quote, search, or analyze a YouTube video, since the model cannot watch video') and constrains it to one video per call. No meaningful alternatives exist among the siblings, so no routing exclusion is needed; the only gap is that it does not spell out when NOT to use it.

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