vphone-mcp

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

With no annotations provided, the description carries the full burden. It discloses key behavioral traits: the two-step process (press home, then tap the app), the supported apps list, and the home screen context. This adds valuable context beyond what the minimal input schema provides, though it could mention error handling or performance aspects.

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 appropriately sized and front-loaded: the first sentence states the core purpose, followed by implementation details and a list. Every sentence earns its place by providing essential information without redundancy, making it efficient and well-structured.

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 tool's low complexity (1 parameter, no annotations, but has an output schema), the description is mostly complete. It covers purpose, usage steps, and supported apps. Since an output schema exists, it need not explain return values, but it could benefit from mentioning error cases or app-not-found behavior for full completeness.

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 input schema has 0% description coverage, so the description must compensate. It adds meaning by specifying that the 'name' parameter refers to an app name from the supported list, which clarifies semantics beyond the schema's generic string type. However, it does not detail format constraints (e.g., case sensitivity), leaving some ambiguity.

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 clearly states the specific action ('Open an app from the home screen by name') and distinguishes it from siblings like 'go_home', 'open_app_switcher', or 'tap' by specifying it's for launching apps from the home screen. It provides a concrete list of supported apps, making the purpose unambiguous.

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 explicitly states when to use this tool ('Open an app from the home screen by name') and includes a prerequisite action ('First presses home to ensure we're on the home screen'), which provides clear context. However, it does not specify when not to use it or mention alternatives like using 'tap' directly on an app icon, leaving some gaps in guidance.

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