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

Annotations already declare readOnlyHint, openWorldHint, non-idempotent and non-destructive, so the safety profile is largely covered. The description adds real value beyond them: tab reuse behavior ('goes to the site's open tab, else to a new tab, so the user's own tabs stay') and, since there is no output schema, what the call answers with ('the elements and text in view, with the same numbers'). It does not address auth/permission needs or failure modes for an open-world 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?

Front-loaded with the action and the 'Call it first' instruction before elaboration, and most sentences carry distinct information (environment, tab reuse, return shape). The trailing list of Moxie actions is useful routing context but is the least essential part and slightly dilutes an otherwise tight description.

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 two-parameter, open-world opener with no output schema, the description covers the environment, the ordering, the tab behavior, and the shape of the response. Auth specifics and what happens on an invalid or unreachable URL are the notable omissions.

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%, so both `app` and `url` are fully documented in the schema and the baseline is 3. The description adds only indirect meaning (that the URL lands in an existing or new tab) and does not restate or extend the `app` slug rule.

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 ... and opens `url`') and immediately clarifies the environment (a real Chrome where the user is signed in), which is the key distinction from a headless fetch. 'Call it first' positions it against the sibling browser_* tools without ambiguity.

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?

Gives explicit ordering guidance ('Call it first') and names the concrete workflows it serves in Moxie (Book appointment, Reschedule appointment, List clients, Find lapsed clients, List memberships), which tells the agent when to reach for it. It stops short of naming a when-not-to-use condition or a direct alternative.

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