Open URL

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

Annotations provide destructiveHint: true, which already signals potential side effects. The description adds no extra context about behavior beyond the obvious action. It does not mention whether a browser must be installed, if the URL will replace current content, or what happens on failure.

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?

Single, front-loaded sentence of 8 words with no extraneous information. Every word earns its place, providing clarity without verbosity.

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?

While annotations and schema cover basic safety and parameter info, the description lacks details like required permissions (e.g., internet access), dependencies on installed browsers, or behavior if the device is locked. For a simple action, this may suffice but leaves gaps.

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% and includes helpful descriptions: the device parameter explicitly directs to use mobile_list_available_devices, adding value beyond the parameter name. The url parameter description is basic but sufficient.

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 clearly states the verb 'Open', the resource 'URL', and the context 'in browser on device'. Among sibling tools, none other perform URL opening, making it immediately distinguishable.

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?

No guidance on when to use this tool versus alternatives (e.g., using mobile_launch_app for a browser, or mobile_click to navigate). No prerequisites or exclusions are mentioned, leaving the agent to infer usage context.

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