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

Annotations cover the safety profile (readOnlyHint=true), so the bar is lower, and the description still adds useful behavioral context: it lists what is returned (performance vs. usual, drop-off, discovery source, comments) and clarifies no user input or authorization setup is needed. No rate limits or pagination behavior mentioned, keeping it short of 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?

Front-loaded with purpose, then usage, then parameter semantics. It is long, but the redundant-looking synonyms each serve query matching, and there is no filler prose. Slightly overstuffed at the tail.

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 steps up to describe return contents and the zero-input requirement, which is exactly what the agent needs. The only hole is the unexplained `title` parameter, which keeps this from being fully 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?

It adds real meaning for `video` (title or partial title accepted; empty = most recent upload), but the second parameter, `title`, is never mentioned even though the description says to pass a title via `video`. At 50% schema coverage this leaves the agent to guess the role of `title`, which can create ambiguity.

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 (deep dive/analyze) and resource (ONE specific YouTube video of the signed-in user's own channel) with explicit scope. It names the relevant siblings (audit_channel, diagnose_channel, find_best_videos), so an agent can route to it 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?

Enumerates rich trigger vocabulary (flopped, tanked, underperformed, blew up, went viral, break down, review), covers the 'my last/latest/newest upload' case, and gives explicit exclusions naming the alternatives for other scopes. It even resolves the ambiguous reference ('that video' = most recent upload) and forbids stopping to ask.

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