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

No annotations exist, so the description carries the full behavioral burden. It discloses the credit/cost model ('1 credit the first time it is added to this account's library; repeat reads are free'), the cache bypass effect via fresh, and the output-size consequence of include_segments. It does not address failure modes (e.g. no transcript found) or auth requirements, preventing a 5.

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?

Four dense, front-loaded sentences with zero filler. The first sentence states the core purpose, the second covers acceptable inputs, the third covers cost/caching, the fourth covers the one parameter that changes output size. Every sentence earns its place.

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 moderately simple tool (4 params, 100%% schema coverage, no output schema/annotations), the description covers the what, the accepted input formatst, the metadada returned, and the credit/caching model. Missing edge-case details like behavior when a video has no transcript are minor for such a small tool, so it does not quite reach 5.

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 baseline is 3. The description adds genuine meaning beyond the schema: it explains which URL formats the video parameter accepts, the practical tradeoff of include_segments ('much larger output'), and the caching/cost semantics that clarify the fresh parameter. This extra context pushes it above baseline.

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?

Uses a specific verb + resource: "Fetch the full transcript of one YouTube (or TikTok) video as clean text with metadata". The singular scope ('one...video') clearly distinguishes it from the sibling get_transcripts (plural), and the metadata list (title, channel, duration, upload date, language) tells the caller exactly what to expect without opening the schema.

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?

Provides clear usage context by enumerating the accepted input forms (watch URL, youtu.be link, Shorts URL, or bare 11-character id) and by giving an explicit condition for include_segments ('only when per-line timestamps are needed'). It does not explicitly name sibling alternatives or exclusions (e.g. when to prefer get_transcripts), which keeps it short of a 5.

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