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 behavioral burden and does not meet it. It never says whether tel: actually initiates a call, whether geo: hands off to a maps app, whether the device must be unlocked or already selected via select_device, or what the call returns on failure. The scheme examples hint at side effects but do not disclose them.

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?

One sentence, front-loaded with the verb and resource, with the scheme examples parenthesized rather than sprawling. 'On the phone' is not filler here since the sibling set includes list_devices/select_device, so it clarifies the target device.

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 one-parameter tool with no output schema the description is nearly adequate, but with no annotations and no schema descriptions at all, it should still say whether the target device must be selected first and roughly what a successful versus failed invocation does. Those omissions matter in a device-control context.

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% — the single 'url' parameter is a bare string with no description. The description partially compensates by listing accepted schemes (https://, tel:, geo:, whatsapp://), which is real meaning beyond the schema, but it gives no format rules, encoding guidance, or failure behavior for malformed input.

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 ('a URL or deep link') and enumerates example schemes (https, tel, geo, whatsapp), which makes it clearly distinct from the app-launching sibling open_app. It stops short of naming that sibling explicitly, but the scheme examples do most of the disambiguating work.

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?

Usage is only implied: the scheme examples suggest when this is appropriate (web links, phone numbers, map coordinates, app deep links) as opposed to open_app for launching packages. There is no explicit statement of when not to use it, no prerequisite such as device selection or unlocked screen, and no alternative named.

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