Open URL

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

With no annotations, the description carries the full burden, and it does disclose a real behavioral trait: it delivers no touch event, so it is immune to slow touch delivery. It omits other important behavior such as what happens on an invalid or unhandled URL, whether the target app must be installed, and what the call returns.

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?

Two sentences, front-loaded with the action and its input form, followed by a performance rationale. Every clause adds usable information and nothing is padded.

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 simple two-parameter tool with no output schema, this covers purpose, input form, and a genuine cost/performance consideration. The remaining gaps, device identification and error/return behavior, are minor but non-trivial since no output schema exists to fill them in.

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 0%, so the description must compensate. It usefully illustrates the 'url' format with two concrete schemes and 'active device' hints that 'device' defaults, but it never explains how the 'device' parameter is identified or formatted, leaving half the parameters undocumented.

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) and resource (deeplink or universal link) with concrete URL examples (myapp://screen, https://…), making the input shape immediately obvious. It does not explicitly distinguish itself from the related sibling 'navigate', though the 'cheapest way to reach a screen' phrasing hints at that trade-off.

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 'usually the cheapest way to reach a screen' remark implies when to prefer this over touch-driven tools like tap, but no alternative is named and no when-not condition is given. The agent must infer the decision rule rather than being routed explicitly.

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