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

Annotations already declare readOnly, openWorld, non-idempotent, non-destructive, so the safety profile is covered. The description adds genuinely non-structured behavior: tab targeting (existing tab vs new tab), preservation of the user's own tabs, and the fact that it returns the resulting page contents with element numbers. That return behavior is valuable since there is no output schema.

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-loads what the tool is, then the imperative 'Call it first', then behavioral detail, then applicability. Sentences are dense but each carries information. The MassageBook action list is slightly list-like padding, though it does aid routing to the related appointment tools.

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 only two optional parameters and no output schema, the description covers what the tool does, when to call it, tab behavior, and what comes back. The phrase 'with the same numbers' is slightly cryptic without knowing the element-numbering convention shared by click/type, but the intent is inferable from siblings.

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 description coverage is 100%, including the nuanced 'leave `app` out unless cotlet_app_guide names an app's own Cloud Browser' rule, so the schema already does most of the work. The description adds the signed-in-user context and the URL tab-routing semantics, which is modest added meaning over baseline.

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: starts the user's Cloud Browser (a real signed-in Chrome) and opens `url`. The parenthetical clarifies what the browser actually is, which matters for an agent reasoning about session state. It does not explicitly differentiate itself from the sibling `cotlet_browser_navigate`, though 'Call it first' implies an entry-point role.

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?

'Call it first' gives a clear ordering rule, and the tab-reuse sentence ('goes to the site's open tab, else to a new tab, so the user's own tabs stay') tells the agent what to expect without extra steps. It also names the MassageBook actions this entry point serves, which helps routing. There is no explicit statement of when NOT to use it versus `cotlet_browser_navigate`.

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