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

With readOnlyHint=true already declaring the safety profile, the description adds real behavioral context: the hasDesignSystem:false empty case and the note that buttonCss is already emitted on the page and only needed to read appearance. It does not describe pagination or sizing, but for a read-only token fetch this is solid added value.

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 tightly packed sentences, front-loaded with what the tool returns before the usage rule. The "Rules:" clause is useful but slightly compresses a prerequisite and a how-to into the tail, leaving minor density.

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-required-param, read-only getter with no output schema and a fully documented single parameter, the description covers return content, empty state, and consumption pattern. Only the absence of any check on when NOT to use it (e.g., before a design system exists) leaves a small gap.

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% and the schema already explains buttonStyles vs buttonCss in detail, so the description adds essentially nothing about the include parameter. Baseline 3 is appropriate when the schema does the heavy lifting.

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 (get) and resource (the site's design system), then names the actual payload — colour tokens, typography, button variants with their CSS variable/class — plus the empty-state shape (hasDesignSystem:false). An agent can distinguish it from create-design-system/save-design-system without opening either schema.

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?

"Call it before styling a block" gives clear when-to-use context, and it prescribes how to consume results (use var(--fabrement-*) and .fabrement-btn--<variant>). It adds a prerequisite (read the design-system-contract skill doc first). No explicit when-not or named alternatives, which keeps it at 4 rather than 5.

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