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

Annotations already provide readOnlyHint and destructiveHint, but the description adds significant behavioral context: API key requirement, credit cost per call, error behavior for videos without captions, and a rate limit. This goes well beyond the structured annotations.

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?

Three sentences, no wasted words. The core purpose is front-loaded, followed by cost/rate-limit caveats and error behavior. Each sentence adds value.

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 single-parameter read-only tool with an output schema present, the description covers input, behavioral safety, cost, error conditions, and rate limits. There are no significant gaps given the structured fields.

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 single parameter 'video' is fully described in the schema (100% coverage), including accepted formats. The description does not add extra parameter-specific details, but the schema carries the semantic load, so a baseline score of 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 uses a specific verb ('Get') with a clear resource ('full transcript of a single YouTube video') and output format ('timestamped markdown'). It distinguishes from siblings by emphasizing 'single video' vs channel/playlist tools.

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 context for when to use (single video) and practical guidance about credits and reusing transcripts. Does not explicitly name sibling alternatives for multi-video scenarios, but the 'single video' phrasing implicitly differentiates.

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