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

Annotations already declare read-only, idempotent, open-world, and non-destructive behavior. The description adds valuable behavioral constraints: variants change exactly ONE element and are grounded in patterns measured on the channel. It also clarifies that the tool focuses on what to test, not whether to test, which is useful beyond the annotations.

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?

The description is two sentences, front-loaded with the primary action and constraints, followed by a clear usage guideline. Every sentence earns its place with no filler or redundant information.

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?

Given the tool's moderate complexity, strong annotations, and complete schema, the description covers the essential context: what it does, when to use it, and key constraints. It does not describe the output format or number of variants, but the purpose implies a list of title variants. With no output schema, this slight gap is acceptable because the behavior is well understood from the description.

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. The description does not add extra parameter-level meaning beyond what the schema already provides (e.g., channel can be a handle, URL, ID, or name; title is optional). The mention of 'patterns measured on that channel' implicitly relates to the channel parameter but adds no syntactic or semantic detail not already in 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?

The description clearly states the tool's function: it suggests title variants for YouTube's Test & Compare, with each variant changing one element and grounded in channel patterns. This is specific and goes beyond a generic verb. It distinguishes from siblings by contrasting 'what to test' with 'whether to test,' though it does not name an alternative tool 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?

The description provides explicit usage context: 'Use this when a creator has a video ready and wants to know what to test rather than whether to test.' This tells the agent when to invoke the tool, though it does not name specific alternatives or exclusions beyond the conceptual distinction.

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