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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds a genuine behavioral trait by disclosing the per-call cost ('호출당 20포인트'), but says nothing about pagination, result caps beyond count, or response shape.

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?

Purpose and returned fields are front-loaded in the first sentence. The Korean sentence is a near-verbatim translation, which doubles length without adding information, but the structure remains clear and scannable.

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?

With no output schema, the description usefully enumerates the returned channel fields and the four tab types. The only notable gap is the absence of any statement about result pagination or how count interacts with the listed items.

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 description coverage is 100%, with the enum, count range, and the accepted channel formats (URL, @handle, UC... ID) all documented in the schema. The description only restates the tabs and returned fields, adding no syntax or format detail beyond the schema, so the 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?

States a specific verb ('look up') and resource ('YouTube channel') and enumerates the returned fields (name, handle, subscribers, description) plus the tab-listing capability. An agent can distinguish it from the many sibling search/download tools, though it never explicitly names an alternative for sibling routing.

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?

The description says what it does but never states when to use it versus alternatives like youtube_search, youtube_metadata, or youtube_playlist. No prerequisites, no exclusions, no indication that 'channel' must already be known.

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