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

Beyond the annotations (readOnlyHint, idempotentHint, non-destructive), the description discloses exactly what gets modified (comments, whitespace), what is preserved (quoted strings, calc() spaces), and what the response includes (minified CSS plus before/after byte sizes). This gives the agent full visibility into how the transformation behaves and what to expect.

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 tightly-packed sentences. The first sentence gets straight to the action and core behavior, the second covers return value and a source reference. No filler or repetition; every sentence earns its place.

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 single-parameter, read-only, idempotent tool with an output schema available, the description covers what the tool does, what it preserves, what it returns, and even cites the algorithm source. An agent has all the information needed to select and invoke this tool 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 has 100% coverage with a clear description for the only parameter, 'css' ('The CSS source to minify'). The tool description adds no additional parameter-specific meaning beyond what the schema already provides, so the baseline of 3 applies.

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 first sentence names the exact action ('Minify CSS') and the resource ('CSS'), and even details the transformation rules (removing comments/whitespace, preserving quoted strings and calc() spaces). This clearly distinguishes it from sibling formatting/minification tools like HTML escape, JSON formatter, or simple whitespace removers.

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 makes the use-case obvious: use this when you need to minify CSS. It doesn't name alternatives or explicit when-not-to-use conditions, but given the sibling list contains no other CSS minifier and the name/title align, this is clear context without needing exclusions.

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