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

Beyond the annotations' mutation and safety hints, the description discloses the initial empty state, the paid-plan requirement, and the shared cap of 10 lists including the blacklist. It does not explain the error behavior when the plan or limit requirement is unmet, but these are meaningful behavioral details for a simple creation tool.

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 front-load the operation and then provide distinct eligibility and capacity constraints. There is no boilerplate or unnecessary wording.

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?

For a one-parameter creation tool, the definition covers the action, initial state, plan requirement, and capacity limit, while the schema fully documents invocation. More detailed failure behavior would be optional rather than necessary for correct tool selection and use.

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?

The sole name parameter is already required, typed, length-limited, and described in the schema, giving 100% schema coverage. The description adds no further naming conventions or semantics, so the baseline score of 3 is appropriate.

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 states a specific action and resource: creating an empty watchlist. Specifying that it starts empty helps distinguish it from addToWatchlist, which populates a watchlist rather than creating one.

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?

"Paid plans only" provides an eligibility prerequisite, while the 10-list limit explains an important constraint on when creation is available. It does not explicitly route agents to listWatchlists for checking existing lists or addToWatchlist for adding entries, so alternative-tool guidance remains incomplete.

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