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

Annotations already cover safety (readOnly, idempotent, non-destructive), but the description adds genuinely new behavioral context: that this is not a full CSS parser and output should be visually verified. That caveat about imperfect fidelity is exactly what an agent needs and cannot get from annotations.

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 short sentences, front-loaded with the core action and followed by the scope limit and the fidelity caveat. No padding or repetition.

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 one-parameter, no-output-schema read-only tool, the description covers purpose, scope boundary, and the key caveat about output fidelity. Nothing an agent needs to invoke it correctly is missing.

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?

There is a single parameter with 100% schema description coverage, including the 4096-character limit, so the schema does all the work. The description adds no format or syntactic detail beyond it, making baseline 3 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 and resource ('Reduce whitespace in CSS snippets'), and the resource name distinguishes it from the minify-html and minify-js siblings without needing further explanation. It stops short of explicitly contrasting its scope with those siblings, so it's clear but not fully differentiated.

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?

'Use for basic stylesheet cleanup rather than production minification' gives both a when-to-use and an explicit when-not-to-use, which is real routing guidance. It doesn't name a sibling alternative for the production case, so it's short of a 5.

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