Open an http(s) URL

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

Annotations already declare readOnlyHint=false, idempotentHint=false and destructiveHint=false, so the safety profile is largely covered. The description adds the useful scheme-validation behavior, but says nothing about which app handles the intent, foreground changes, or failure behavior for a non-idempotent 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?

Two short sentences, zero filler, with the core action and the scheme restriction front-loaded. Every clause carries information an agent needs.

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?

With an output schema present, return values need not be described, and the description covers the action, accepted schemes, and display targeting for a 3-parameter tool. Minor gaps remain around required device/serial handling and failure modes, but nothing essential to invoking it correctly is missing.

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 67%: serial and displayId are documented in the schema, while url carries only length bounds. The description adds the meaningful constraint that url must be http/https, partially compensating, but 2048-char limit and display semantics add nothing beyond the schema. Baseline 3 fits.

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 action ('Start ACTION_VIEW') and resource ('http or https URL'), and narrows scope to one logical display. It is distinguishable from siblings like mobile_app_launch or mobile_input_tap, though it never names an alternative sibling, so it stops short of a 5.

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 scheme restriction ('http or https... others rejected') implies when the tool is valid, but there is no explicit statement of when to prefer this over mobile_app_launch or other navigation-oriented siblings, and no prerequisites such as requiring an unlocked device.

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