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

Annotations already supply the full safety profile (readOnlyHint, openWorldHint, idempotentHint, destructiveHint=false), so the bar is lower. The description's behavioral additions (20-result cap, returned fields) largely duplicate the schema's maxRows description and the existing output schema, so it adds only modest value beyond structured data.

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 tight sentences, front-loaded with the verb and resource, then return shape, then usage and the sibling routing. No filler or redundant phrasing.

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 an output schema present the description needn't enumerate return fields, and annotations handle the safety profile; the description still covers scope, result limits, use intent, and the sibling alternative. Nothing needed to invoke it correctly is missing.

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%, so the baseline is 3, but the description supplies concrete query examples ("n8n automation tutorial", "best budget laptops 2026") that clarify the intended free-text style beyond the schema's "exactly as you would type them into YouTube" wording, and restates the 20-row ceiling in the context of results.

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+resource ("Search YouTube for videos by keyword") with concrete example queries, and explicitly distinguishes itself from the sibling youtube_channel_videos. An agent can tell it apart from the channel-scoped alternative without opening either 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?

Names explicit use cases (content research, finding competitors, spotting popular topics) and routes the agent to the alternative when the intent is channel-scoped: "To list videos from one specific channel use youtube_channel_videos instead." When-to-use and when-to-use-something-else are both covered.

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