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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description adds genuine interactive behavior (keys light up on register, a running count of keys received), but says nothing about whether a session/UI is opened, whether it blocks, or how the interaction ends.

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?

Three short, front-loaded sentences with no filler; the capability is stated first and the interaction model second. The closing sentence about returning keys and labels is slightly redundant given an output schema exists, but it costs little.

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?

With one optional parameter, full schema coverage, an output schema and rich annotations, the description only needs to convey the interactive nature — which it does. Remaining gaps (session lifecycle, blocking behavior) are modest for a read-only tester.

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% and the layout property already documents accepted shapes, sizes and the default default of 'ANSI US, full size'. The description's 'such as ANSI US or ISO UK' merely mirrors the schema examples rather than adding format rules or fallback behavior.

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?

States a concrete verb and resource ('Opens a keyboard tester') plus the scope ('for a board layout such as ANSI US or ISO UK'), which is specific enough to distinguish it from a layout lookup. It does not, however, contrast itself with the close sibling start_typing_test, so an agent must infer the difference from names alone.

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 explains what the tester does but gives no when-to-use guidance, no prerequisites, and no exclusions relative to siblings like start_typing_test or check_rollover. An agent must guess that this is the interactive per-key visual test rather than a typing-speed or rollover check.

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