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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so safety is covered structurally. The description still adds real value: it commits to never raising a protocol error and specifies the exact error envelope shape and an example message, which no annotation conveys. It goes beyond the structured fields, so it earns more than a bare baseline.

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?

Front-loaded with the verb and scope, then checks, then return shape, then exclusions and error behavior — logical ordering with no truly wasted sentences. Slight redundancy between the input example and the error example keeps it just short of maximally tight, and the bare 'FREE' fragment adds little.

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?

Return shape is described (though an output schema exists), error behavior on malformed input is spelled out, the input expectation is unambiguous, and the alternative tool is named. Nothing an agent needs in order to call this 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?

Schema coverage is 100% for the single 'content' parameter, so the schema already documents type, minLength, and requiredness, and the baseline of 3 applies. The description's 'Typical input {"content": "<full SKILL.md text>"}' is a concrete example that confirms the whole-file expectation, a marginal addition on top of the schema.

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 ('lint one SKILL.md file') and enumerates exactly what is checked: frontmatter fields, description quality, body structure, secret leakage, injection phrasing, size budget. It also names the sibling it is not for (packaging_check), so an agent can route without opening a 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?

Gives explicit scope ('Use on the full text of one SKILL.md') plus an exclusion and the alternative to use instead ('Not for the surrounding archive layout (packaging_check)'). No inference required to pick this tool over its siblings.

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