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

Annotations already establish readOnly, idempotent, and non-destructive, so the safety profile is covered. The description adds genuinely useful behavior beyond that — the $0.01 cost and the underlying GET route — but says nothing about the payment retry flow or rate limits, which the schema handles instead.

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 terse fragments with zero filler, and the most decision-relevant content (what metadata, at what price) is front-loaded. The telegraphic style is efficient, though the endpoint fragment borders on noise for an agent that cannot issue raw HTTP calls.

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 single-resource read tool, the essentials are present: the returned fields are listed despite there being no output schema, safety is covered by annotations, and cost is disclosed. The main gap is the absence of any pointer to the closely related transcript and channel tools.

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 the url parameter and the payment/x402 proof flow fully documented in the schema itself. The description's '?url=' fragment merely restates the parameter name and adds no format, edge-case, or validation detail beyond it; baseline 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?

Names the resource (a YouTube video) and enumerates exactly what is returned — title, channel, views, length, description — so the agent knows this fetches video metadata rather than a transcript or channel listing. It does not explicitly distinguish itself from siblings like get_youtube_transcript or get_youtube_channel, leaving that to the name alone.

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?

There is no when-to-use guidance at all: nothing says to prefer this over get_youtube_transcript when a transcript is wanted, or over get_youtube_search when only an ID is known. The only contextual hint is the price/endpoint fragment, which describes an execution detail rather than tool selection.

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