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

With no annotations provided, the description carries the full responsibility for behavioral disclosure. It reveals the key nuance that the virtual pad is a real HID device, that it reads device state rather than browser state, and that the `gamepad` field's `registered` flag is the authoritative presence signal. This goes well beyond a generic status-tool description.

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?

Every sentence earns its place: the opening states the core purpose, the second explains the unusual HID behavior, the third provides output-field guidance, and the final sentence prevents a common misuse. It is dense but not bloated, and the critical caveat is front-loaded.

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 and the absence of an output schema, the description adequately explains what the caller will see (`gamepad` field, `registered`, surrounding HID surfaces) and what it will not see. The behavior, scope, and expected interpretation are all covered well enough for an agent to call and interpret the tool correctly.

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 schema already fully documents the single `udid` parameter with 100% coverage, so the baseline is 3. The description adds useful device context but does not add parameter-specific guidance beyond what the schema provides.

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?

Begins with a specific verb and resource: 'Report whether a virtual game controller is currently registered on an iOS device.' It also differentiates itself from related tools like ios_gamepad_state by explicitly stating it reports presence, not the last axes/buttons sent, making the tool's scope unmistakable.

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 gives clear context for when to use the tool: it reads the actual device rather than a web page and stays valid with no browser open. It also tells the agent what not to expect ('reports presence, not the last axes/buttons') and directs value confirmation to the app under test, though it does not explicitly name alternative sibling tools.

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