youtube_video_facts

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

With no annotations provided, the description carries the full burden. It discloses that the tool is cheaper than transcript retrieval, the exact data it returns, and that it does not read captions in the first sentence. It does not cover edge cases like unavailable videos, but for a simple read-only lookup, the transparency is solid.

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 compact and front-loaded with the primary purpose. Every sentence adds value: the first sentence defines the action, the second enumerates return fields, and the third gives usage context. There is no redundancy or filler.

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 simple one-parameter metadata lookup tool with an output schema, the description is complete. It covers what the tool does, what data it returns, and when to use it relative to sibling tools. The presence of an output schema means return format details need not be repeated here.

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 schema already provides a complete description for the single 'url' parameter (100% coverage). The description does not add extra meaning about the parameter beyond what the schema states, but it is not lacking since the schema is sufficient.

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 tool looks up YouTube video metadata without reading captions. It lists specific data fields (title, channel, duration, publish date, counts, etc.) and differentiates from the sibling youtube_transcript by framing it as a metadata lookup rather than a transcript fetch.

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?

Explicit guidance is given: use this tool when the question is about the video itself, not its contents, and to check for captions before requesting a transcript. It also mentions the cost advantage over pulling a transcript, effectively saying when to prefer this tool over youtube_transcript.

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