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

Beyond the annotations, it discloses that the tool waits for the load to finish, errors on native mobile sessions, and returns confirmation rather than the page. This tells an agent what to expect after invocation and which follow-up tools are needed.

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 purpose is front-loaded in the first sentence, and the remaining sentences each add distinct value: scope, return semantics, follow-up tools, sibling differentiation, and the former alias. There is no wasted text.

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?

The description covers what the tool does, when it applies, its error condition, its return shape, and the relevant alternatives, while the annotations carry the safety profile and the schema carries the parameters. No output schema exists, and the description explicitly explains what the return value is and is not.

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 the schema already documents both sessionId and url. The description does not add meaningful syntax or format details beyond the schema's own parameter descriptions, making the baseline 3 appropriate.

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 states a specific verb and resource: 'Drive a browser session to a URL and wait for the load to finish.' It immediately scopes the tool to browser sessions and distinguishes it from web_navigate, ios_safari_navigate, and device_navigate_url by the sessionId addressing.

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 explicit when-to-use guidance ('Browser sessions only — a native mobile session has no address bar and this errors there') and names the alternatives for other contexts: web_navigate by pageId and ios_safari_navigate / device_navigate_url by udid. It also recommends follow-up tools for reading the page after navigation.

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