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

The description adds real value beyond annotations: an explicit cost model (2 credits per call, 0.1 for a failure) that the agent cannot get from readOnlyHint/openWorldHint, and a concrete statement of what is returned in lieu of an output schema. Missing are any notes on failure/error conditions for private or age-restricted videos.

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 dense sentences with the resource list front-loaded, the input-type scope second, and the cost caveat last. Nothing is redundant or padded.

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 tool with no output schema, the description supplies the return contents and the credit cost, which is what an agent needs to call it responsibly. Only edge-case behavior (invalid URLs, unavailable formats, partial failures) is left unexplained.

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% with a single 'url' parameter, so the baseline is 3; the description earns an extra point by clarifying what kinds of links are acceptable (video, Short, or community post), which the schema's 'link as copied from the app or the browser' does not spell out. The dangling 'is_post' reference slightly muddies whether URL type is auto-detected or supplied.

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?

Specific verb 'Get' plus an enumerated resource set (title, author, duration, thumbnails, formats with file sizes) and clear scope covering both YouTube videos/Shorts and community posts. An agent can distinguish this metadata tool from youtube_download or youtube_search without opening any schema.

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?

Usage is implied by the accepted URL types, so the agent knows to call it with a video or post link to obtain metadata. However, no alternative is named (e.g., youtube_download for downloading, youtube_search for discovery), and the reference to 'is_post' as something that 'says which' is confusing since no such parameter exists in the schema.

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