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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuine context beyond that: it opens an interactive view, reports two specific measurements, and renders a full-size ANSI board. It stops short of saying whether the view blocks the session or how the test terminates, which keeps it off a 5.

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?

Two sentences, front-loaded with purpose and then output shape, with no filler. The second sentence is slightly overloaded by mixing the return format and the no-input note, but nothing is wasted.

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?

For a zero-parameter tool with a full annotation set and an output schema, the description covers what the test does and what it displays. What is missing is routing information: an agent facing open_keyboard_tester and start_typing_test has no stated basis for picking check_rollover specifically.

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 takes zero parameters, so per the baseline this is a 4. The description also confirms the zero-input nature ("no inputs needed"), which is consistent with the empty schema rather than adding anything contradicting it.

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 specific verb and resource ("Opens a rollover test") and immediately defines what the test measures: simultaneous keys held and the maximum number the keyboard registered together. That is concrete enough to separate it from the generic open_keyboard_tester, though it never names the sibling to draw the contrast explicitly.

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 only implied — an agent can infer this is the tool for diagnosing N-key rollover / key-ghosting limits. There is no explicit when-to-use versus open_keyboard_tester or start_typing_test, and no stated preconditions beyond "no inputs needed."

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