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

Annotations already cover read-only, idempotent, and non-destructive behavior. The description adds meaningful context beyond annotations: it returns the reasons and enforces the installer's actual compatibility rules, so the answer matches reality. This gives the agent useful behavioral expectations without contradicting any annotation.

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 concise sentences: the first states the purpose and required inputs, the second gives usage guidance and the benefit. Every sentence earns its place with no fluff or redundancy.

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 simple, well-schema-documented tool with four rich annotations, the description covers the task, inputs, output (reasons), and the reason this tool should be trusted. There is no output schema, but the description explicitly says the return will include reasons, giving enough context for an agent to invoke and interpret it.

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 description repeats only that the tool uses 'macOS version and CPU architecture,' which maps directly to os_version and arch. It adds no new parameter meaning beyond the schema, so the baseline of 3 is appropriate.

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 ('Decide'), the exact resource (a specific Mac running Yappy), the inputs (macOS version and CPU architecture), and the output (reasons). This clearly differentiates it from the sibling get_system_requirements, which would provide general requirements rather than a compatibility verdict.

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?

Explicitly recommends using this tool instead of manually reasoning about requirements, and explains why: it encodes the same rules the installer uses. It does not name sibling alternatives or state when not to use it, but the guidance strongly narrows when the tool is appropriate.

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