List fonts for a platform

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

The description goes beyond the readOnlyHint annotation by adding that the fonts 'genuinely exist on the given OS', implying an actual system query rather than a static list. It also discloses that each record contains a `font` property, giving insight into the return structure. No negative side effects are mentioned, but the readOnly annotation covers that, and the openWorldHint aligns with OS-dependent results. This is valuable additional context.

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 two sentences with no redundancy. The first sentence front-loads the core purpose, and the second provides actionable usage instructions. It is concise and well-structured, earning a perfect score.

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 read-only tool with one enum parameter and no output schema, the description is nearly complete. It explains the purpose and gives a practical usage example (how to configure profile fonts). It does not detail the entire return format, but the mention of 'each record' implies an array of objects, which is sufficient for an agent to understand the tool's output and use it correctly.

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 input schema defines `platform` with an enum of windows/macos/linux, but the description does little to explain the parameter beyond saying 'given OS'. It implicitly maps platform to OS, but does not elaborate on each value or how the choice affects results. Since schema coverage is 0%, the description should compensate more, but the enum is self-explanatory and the parameter is simple, so the gap is minor.

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 clearly states the tool's purpose: 'List font families that genuinely exist on the given OS.' It specifies the resource (font families) and the scope (OS-dependent), distinguishing it from sibling list tools like list_statuses or list_profiles. The verb 'list' is specific and matches the tool name, making the purpose unambiguous.

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 by explaining how to apply the results: 'extract just the `font` property... set that as `fonts`, and set `fontsMode` to `manual`.' This tells the agent when to use the tool (when configuring profile fonts) and how to process the output. It does not explicitly mention alternatives or when not to use it, but no direct alternative exists among siblings, so the guidance is sufficient.

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