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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered. The description adds real value beyond that: it explains the dual meaning of `viewCount` (concurrent vs. total) and warns that YouTube swaps the label, which is exactly the kind of caveat an agent cannot infer. It also states the 1-credit cost.

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 is front-loaded in the first sentence, followed by scope, then a caveat and a cost note. Four sentences all carry information, though the viewCount explanation and the label-swap sentence could be tightened into one.

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 should carry more of the return-shape burden. It addresses the trickiest field (`viewCount`) but says nothing about the overall response structure or how pagination via `cursor` terminates, leaving the agent to discover those by calling.

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 67% — `handle` and `cursor` are documented in the schema, but `cache_max_age` has no description anywhere. The description adds nothing about parameter semantics, so it neither compensates for the gap nor detracts; baseline 3 fits.

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?

The description names a specific resource and scope: a channel's Live tab, covering live-now, scheduled, and finished-but-still-listed streams. That implicitly separates it from youtube_channelVideos and youtube_channelShorts, though it never names a sibling explicitly.

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?

Usage is implied by the 'Live tab' framing rather than stated. There is no explicit 'use this when you want X, use youtube_channelVideos when you want Y' routing, and no note about what happens if a channel has no Live tab.

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