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

Annotations only declare the safety profile (readOnly, openWorld, non-idempotent); the description adds genuinely new behavior: it is a real signed-in Chrome, the URL targets the site's open tab before creating a new tab, the user's own tabs are preserved, and it returns the page's in-view elements and text. That is substantial context beyond the annotations, with no contradiction of readOnlyHint (it reads the page rather than mutating data).

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' directive, and each sentence carries information about behavior, return content, or routing. The closing Timely action list is dense but earns its place by connecting this tool to the timely_* siblings.

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 still explains what comes back ('the elements and text in view, with the same numbers'), and it covers the auth state (user is signed in), tab side effects, and invocation ordering. Nothing an agent needs to call this correctly appears to be missing.

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, but the description adds meaning the schema does not: it explains what happens to `url` (routed to the site's existing tab or a new one). The `app` parameter is left entirely to the schema, which keeps this from a 5.

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 Chrome on Cotlet) and opens `url`. It also distinguishes itself from siblings by telling the agent to 'Call it first' and by scoping the URL to the site's existing tab or a new tab, which reads as the entry point ahead of navigate/click.

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 directive that separates it from the other browser_* tools, and the Timely action list tells the agent which downstream tasks this enables. It stops short of naming an explicit when-not or naming the sibling to use for subsequent navigation, so a small gap remains.

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