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

Annotations already declare readOnlyHint and idempotentHint, so the safety profile is covered. The description adds behavioral context by detailing exactly what the response includes (source, parameters, usage example), which is valuable given the absence of an output schema.

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 a single sentence that front-loads the action and resource, then succinctly lists return contents. Every phrase earns its place, with no redundant or filler information.

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, single-parameter tool with robust annotations, the description is complete. It tells the agent what the tool does, what input is needed, and what output to expect, which is sufficient for selection and invocation without an output schema.

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 schema fully documents the single 'id' parameter with format (kebab-case) and examples. The description only restates that lookup is by id, adding minimal meaning beyond the schema. With 100% schema coverage, a 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?

The description clearly states the action ('Get'), the resource ('SCSS mixin'), and the scope ('by id'), while also specifying the return content (full source, parameters, usage example). This distinguishes it from sibling tools like list_scss_mixins, which serve a different purpose.

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 clearly implies usage when a specific mixin id is known and details are needed, contrasting with listing all mixins via list_scss_mixins. However, it does not explicitly mention when not to use it or name alternatives, leaving the guidance slightly implicit.

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