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

Annotations already cover the read-only, non-destructive, open-world profile. The description goes well beyond them by disclosing the return shape (one block of text plus title and channel), the absence of per-line timestamps, the accepted URL variants, and the exact failure mode for caption-less videos with instructions to report rather than guess.

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 tight sentences, front-loaded with the trigger condition and followed by behavior, constraints, and exclusion. No sentence is filler; each carries a distinct operational instruction.

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?

With no output schema, the description compensates by describing the return payload and its limitations (no timestamps, single text block). Annotations cover safety, so nothing an agent needs to call or interpret this tool correctly is missing.

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, but the description adds genuine meaning: it enumerates the accepted URL forms (watch, youtu.be, Shorts, live) beyond the schema's generic 'full or short URL or 11-character ID'. It is silent on the language and send_metadata parameters, so it falls short of a 5.

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 (retrieve the full spoken transcript of a YouTube video) and immediately scopes it to YouTube, which separates it from every search/list sibling (search_youtube, list_channel_videos, etc.). An agent can tell what it returns 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?

Gives explicit triggering conditions ('user shares a YouTube video link or ID, or asks to summarize, explain, quote, translate, take notes on, or chat about'), explicit exclusions ('non-YouTube videos or files the user uploads'), and a fallback behavior when captions are missing. This is complete routing guidance.

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