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

The description richly discloses behavior beyond annotations: Android dispatches trusted keyDown/keyUp, iOS uses hardware surface or falls back to synthesized isTrusted:false events, focus behavior differs, and form submission is handled. It also notes the `via` response field. This is far more context than the annotations provide.

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 front-loaded with the core action and every sentence adds relevant behavioral detail, but it is a dense single paragraph that could be slightly more scannable. It is appropriately sized for the complexity without being repetitive.

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 cross-platform complexity and fallback mechanics, the description covers what an agent needs to know: platform differences, focus movement, form submission, and the response indicator. No output schema exists, but the `via` response is mentioned, and the annotations cover the safety profile.

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 description coverage is 100%, so the baseline is 3. The description adds no meaning for any parameter (key, udid, pageId, socket, platformVersion) beyond what the schema already documents.

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 verb (press) and resource (key) scoped to the device browser, explicitly covering iOS Safari and Android Chrome. It distinguishes itself from native app key tools by that browser scope, though it does not name a specific sibling alternative.

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?

Usage is implied by 'in the device browser', but there is no explicit when-to-use guidance or comparison to alternatives like device_key or ios_key_hid. No exclusions or prerequisites are given.

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