List YouTube Transcript Languages

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

Annotations already declare readOnlyHint=true, openWorldHint=true and destructiveHint=false, so safety is covered. The description adds value beyond them by disclosing the shape of the result (code, display name, auto-generated flag) and by framing it as what YouTube "currently exposes," signaling that availability is live and may vary per video.

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?

Two sentences, no filler. The purpose and return contents come first, then the sequencing rule against the alternative, which is the correct front-loading order for a discovery tool.

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 one-parameter read tool with full schema coverage and no output schema, the description covers purpose, return fields, and ordering against the sibling. It omits only the empty-result case (video with no captions), a minor gap at this complexity level.

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%: videoIdOrUrl is already documented in the schema as a URL or raw 11-character ID. The description adds no format, validation, or edge-case detail about that parameter, so the schema does the heavy lifting and the baseline of 3 applies.

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 and resource ("Lists the caption languages ... for a video") and enumerates what each entry contains (language code, display name, auto-generated flag). It is clearly differentiated from the sibling transcript tools by naming get_youtube_transcript explicitly.

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?

It gives an explicit trigger and ordering rule: call this before get_youtube_transcript when the user wants a specific language. It does not state the inverse case (skip this and call get_youtube_transcript directly when no language preference exists), so the routing guidance is clear but not exhaustive.

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