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

With no annotations, the description carries the full behavioral disclosure burden and does so thoroughly. It explains that keys are 'pressed AND released as one action, so nothing stays held,' describes the fallback error case ('no HID available'), and documents the release mechanism via an empty list. This is transparent and prevents common misuse.

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 dense but efficient: three sentences cover purpose, parameter semantics, release behavior, and failure modes. Every sentence earns its place, and the core differentiating purpose is front-loaded. No redundant or filler content is present.

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 lack of annotations and output schema, the description covers all critical aspects an agent needs: what the tool does, how to encode usages, chord behavior, the one-action press/release guarantee, the empty-list release usage, and the expected error condition. The tool is complex, and the description is complete enough for correct invocation.

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 100%, so the baseline is 3, but the description adds real value beyond the schema by providing concrete USB HID usage-code examples (0x04=a, 0x28=Return), modifier ranges (0xE0–0xE3), and chord semantics. The udid parameter gains no new meaning, but the usages parameter is substantially enriched.

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 a specific action ('Send raw HID keyboard usage codes as real hardware keypresses') on a specific resource (iOS key input). It strongly distinguishes itself from sibling typing tools by claiming it is 'the ONLY way to inject true keypresses, modifiers and shortcuts,' which separates it from ios_send_keys and similar tools.

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 provides clear usage context: use this when true hardware keypresses, modifiers, chords, or shortcuts are needed, and notes that 'typing tools can only type into a focused field.' It also explains when to pass an empty list to force-release stuck keys. However, it does not explicitly name alternative sibling tools or give a formal when-not-to-use list beyond the generic typing-tool contrast.

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