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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety and external-network behavior are covered. The description adds a genuinely useful non-annotated detail — the "(1 credit)" cost — but says nothing about pagination (cursor/continuationToken round-tripping) or what happens when a channel cannot be resolved.

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 short fragments, front-loaded with the action and scope, with the credit cost appended in parentheses. Nothing is wasted, though the terseness comes at the cost of any usage or pagination context.

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 five-parameter read tool with no output schema, the definition covers purpose and cost but omits that a channel identifier is mandatory and that results are paginated via the returned cursor. The rich schema partially compensates, leaving it adequate but not complete.

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%, so the schema already explains query, cursor, handle, channelId, and continuationToken, including the "Send this or handle" constraint. The description contributes no additional parameter meaning, which is the expected baseline when the schema does the heavy lifting.

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?

"Search inside one channel's videos" gives a specific verb (search) plus a scoped resource (videos within a single channel), which is enough to separate it from a global youtube_search and from youtube_channel_videos. It stops short of naming those siblings explicitly, so the differentiation is inferred rather than stated.

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 phrase "inside one channel" implies the when-to-use case (channel-scoped query rather than site-wide search), but no alternative tool is named and no condition or prerequisite is spelled out. An agent must reason about the sibling list itself to pick correctly.

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