list_video_captions

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

While annotations already indicate readOnly and openWorld, the description adds valuable behavioral context: authentication requirements (API Key or OAuth), the exact return structure (items[].snippet with language, name, trackKind, lastUpdated), and clarifies that it returns metadata not transcript text.

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 concise sentences with no redundancy. First sentence states purpose and authentication; second adds return structure and usage guidance. Every sentence adds essential information.

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?

Given the simple tool (single parameter, no output schema), the description fully covers purpose, authentication, return content, and alternative tool. No gaps remain.

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?

The only parameter `video_id` is fully described in the schema with pattern and description. The description does not add any additional semantics beyond what the schema already provides, so baseline 3 is appropriate.

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 clearly states the action ('list'), the resource ('caption track metadata for a video'), and distinguishes from the sibling tool `get_video_transcript` by specifying its purpose is to discover available languages, not download text.

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 provides when to use this tool ('discover what caption languages exist') and when to use the alternative (`get_video_transcript` for actual text). Also mentions authentication requirement upfront.

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