vphone-mcp

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

No annotations are provided, so the description carries the full burden. It only describes the action ('Tap') without disclosing behavioral traits like what happens after tapping (e.g., opens a keyboard, triggers a search, requires specific permissions), potential side effects, or error conditions. This leaves the agent with minimal insight into the tool's behavior.

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, clear sentence that directly states the action. It's front-loaded with the verb and target, with no wasted words or redundant information. This is appropriately concise for a simple tool.

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 simplicity (0 parameters, output schema exists), the description is minimal but incomplete. It lacks context on what the tool achieves (e.g., opens a search interface), when to use it, and behavioral details. With no annotations and an output schema that might cover return values, the description should do more to explain the tool's role and effects, but it doesn't.

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 tool has 0 parameters, and schema description coverage is 100%, so there are no parameters to document. The description doesn't need to add parameter semantics, and it appropriately doesn't mention any. Baseline is 4 for zero parameters, as it avoids unnecessary information.

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 the action ('Tap') and target ('Search bar on the home screen'), which gives a basic purpose. However, it's vague about what this actually does—does it open a search interface, focus a cursor, or something else? It doesn't clearly distinguish from siblings like 'tap' or 'open_app', which could be used for similar UI interactions.

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?

No guidance is provided on when to use this tool versus alternatives. For example, it doesn't specify if this is for initiating a search versus other ways to access search functionality, or if it's specific to a certain app or system state. The description is purely instructional without context.

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