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

Annotations already declare readOnlyHint=true, so the safe read-only nature is covered. The description adds no extra behavioral context (e.g., rate limits, video availability constraints, or return format). It aligns with the annotation but provides no additional transparency beyond what the annotation already conveys.

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 extremely concise: one clear purpose sentence followed by two brief parameter explanations. It is front-loaded with the key action and resource, and every sentence adds value without redundancy.

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?

The tool has no output schema, so the description should explain the return value. However, it only says 'Extract transcript/subtitles' without specifying the output format (e.g., plain text, timestamped JSON, or whether it returns the full transcript or a portion). This leaves a significant gap for an agent invoking the tool, despite the simplicity of the inputs.

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 0%, so the description fully compensates by explaining both parameters: video_url includes a concrete example URL, and language specifies a default value 'en'. This adds meaning beyond the bare schema definition and would be essential for correct invocation.

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 uses a specific verb 'Extract' with a clear target resource ('transcript/subtitles from a YouTube video'). This distinguishes it from sibling tools like imdb_search and search_podcasts, which are search-oriented and unrelated to video transcripts.

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 clearly implies usage for retrieving YouTube transcripts, but it does not explicitly state when to use this tool vs. alternatives or mention exclusions. Sibling tools are not similar, so there is no explicit comparison, but the intended use case is inferable from the purpose statement.

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