open_url

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It only says 'open' without describing what happens on success or failure, whether it returns any data, or if it is asynchronous. This leaves significant ambiguity for a tool that performs an action.

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 description is a single, front-loaded sentence that is immediately understandable. It is concise with no wasted words. However, it is so brief that it omits crucial details, but for conciseness and structure, it is well-formatted.

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?

Given the lack of annotations, output schema, and minimal parameter descriptions, the description is not complete. It does not explain return values, error handling, or the exact behavior of opening a URL. The agent would need to experiment to understand the tool's full capabilities, making it insufficient for reliable invocation.

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?

The schema covers 50% of parameters with a description for 'serial' but none for 'url'. The tool description does not compensate for this gap, failing to explain what a valid 'url' looks like (e.g., must include scheme) or any formatting requirements. The agent gets no added clarity beyond the bare schema.

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 clear verb ('open') and resource ('URL or deep link') with a location ('in the device'). It is specific enough to be understood, but it does not explicitly distinguish itself from sibling tools like launch_app, which could also open things. Still, the resource type is distinct, so it earns a 4.

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?

The description provides no guidance on when to use this tool versus alternatives. There is no mention of scenarios, prerequisites, or why one would choose this over launch_app or other navigation tools. The agent is left to infer the appropriate context.

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