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

Beyond the annotations (readOnlyHint, openWorldHint, idempotentHint=false, destructiveHint=false), it discloses real behavior: it launches a signed-in Chrome session, reuses the site's existing tab before creating a new one so the user's tabs survive, and returns the visible elements and text of the page afterwards. Those are the non-obvious side effects and return-shape facts an agent needs before calling.

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 core sentences are front-loaded and dense with useful detail, but the trailing sentence listing Fillout actions ('Create form, Add question, Set form logic...') duplicates what the fillout_* siblings already declare and muddies an otherwise tight definition.

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 usefully explains what comes back (elements and text in view, with matching numbers) and how tabs are chosen, which covers the essentials for a session-start tool. It omits failure modes (invalid URL, unavailable browser, session lifetime), which would matter for a tool with zero required parameters and network dependency.

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 both `app` and `url` are already documented in structured form. The description adds the useful tab-targeting semantics of `url` but says nothing about `app` (which the schema explains as 'leave it out'), so it neither compensates nor extends much beyond 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 uses a specific verb and resource ('Starts the user's Cloud Browser ... and opens `url`') and clarifies what the browser actually is (a real Chrome where the user is signed in). The ordering cue 'Call it first' implicitly separates it from navigate/click siblings, but it never names cotlet_browser_navigate, so an agent must infer the boundary itself.

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?

It gives a clear precondition-style instruction ('Call it first') that tells the agent this is the entry point for a browser session, which is real sequencing guidance. It stops short of stating when not to use it or pointing to the alternative for driving an already-open page (e.g. navigate/click).

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