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

Annotations already declare readOnly, openWorld, non-destructive and non-idempotent, so the safety profile is covered; the description adds real value beyond them by disclosing tab-targeting side effects and the shape of the immediate response ('the elements and text in view, with the same numbers'). It does not state session lifetime, auth prerequisites, or what happens if a browser is already open.

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 ordering instruction, and the tab-targeting caveat is stated compactly. The trailing LiveChat action list is only loosely connected to opening a browser and is the least earned sentence in the block.

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, fully documented parameters and no output schema, the description supplies everything an agent needs: when to call it, what url does, how to handle app, and what comes back. Remaining ambiguity about the navigate/open split is a sibling-routing issue rather than missing information about this tool.

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 already 100%, so the baseline is 3; the description earns a bump by explaining the effect of `url` on tab targeting ('goes to the site's open tab, else to a new tab, so the user's own tabs stay'), which the schema does not convey. The `app` behavior is largely duplicated from the schema description rather than extended.

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 clarifies this is a real Chrome where the user is already signed in, which is meaningful scope detail. It does not, however, distinguish itself from the sibling `cotlet_browser_navigate`, which an agent could easily confuse with it.

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 a clear ordering rule ('Call it first') and explains the `app` parameter's exceptional case via cotlet_app_guide. It lacks any explicit when-not or sibling routing, so the boundary with cotlet_browser_navigate and cotlet_browser_read is left for the agent to infer.

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