Open URL

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

Annotations already disclose that the tool is not read-only and has open-world effects, and the description aligns with that. It adds minimal context beyond the annotations — no mention of which browser is used, whether it navigates away from the current app state, or failure conditions.

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?

A single eight-word sentence that front-loads the verb and object with zero filler. Every word earns its place, making it a model of conciseness.

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?

For a low-complexity two-parameter action, the fully documented schema plus side-effect annotations make the definition nearly complete. Remaining gaps are minor: unspecified return behavior (no output schema) and which browser is selected as the target.

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 the device parameter's schema description already points to mobile_list_available_devices, which is strong guidance. The tool description adds no parameter-specific detail, so the baseline of 3 is 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?

States a specific verb (open), resource (URL), and target (browser on device), which distinguishes it from siblings like mobile_launch_app (apps) and mobile_press_button (UI interaction). Slightly generic phrasing, but unambiguous about the action it performs.

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?

Provides no guidance on when to use this tool versus alternatives. Nothing tells the agent to prefer this over launching a browser via mobile_launch_app, or whether a browser must already be installed on the target device.

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