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

Annotations already declare readOnly and non-destructive, so the description is free to add the valuable extras it does: result ordering (newest first), returned fields (titles and durations), and a concrete quota model ('Free plan: 10 a day, then 1 credit'). It omits pagination behavior and what happens when a channel exceeds the limit, which keeps it below a 5.

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 short sentences, each doing distinct work: capability, accepted inputs, cost, and next step. No filler, and the core capability is front-loaded.

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 compensates by naming the returned fields and ordering, and it discloses the quota that governs repeated calls. Minor gaps remain around pagination and the default limit, but nothing essential to invoking 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 adds real meaning about accepted input forms for 'url' ('playlist links or IDs and channel links or @handles') that an agent would otherwise have to infer. The 'limit' parameter is left entirely to the schema.

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 and resource ('List the videos in a YouTube playlist, or a channel's uploads') plus scope details (newest first, titles and durations). An agent can distinguish it from search_youtube and summarize_video 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?

Gives an explicit follow-on path ('Use get_transcript on the videos you need'), which routes the agent into the sibling tool for transcript work. It does not state when to prefer search_youtube over this listing tool, so it falls short of full when/when-not guidance.

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