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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, and the description partly restates that ('read-only and idempotent'). The genuine added value is the error contract: it never raises a protocol error and instead returns an error object describing the fix, which makes retry-after-correction safe. That is real behavior the annotations cannot express; the mild repetition of the safety hints keeps it from a 5.

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?

Purpose and exclusions are front-loaded and well ordered, but the block is longer than needed: the return-shape example duplicates an existing output schema, and 'FREE' plus the retry sentence add bulk around an otherwise tight core. Structure is good; economy is only fair.

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?

With an output schema present, the description need not explain return values, and annotations already cover the safety profile. What remains — scope, the sibling boundary, the input expectation, and the non-throwing error contract — is fully stated, so an agent can call this correctly on the first attempt.

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 required parameter with 100% schema description coverage ('Full text of the skill file, system prompt, or tool description to audit'), so the schema already carries the semantics. The description's inline example echoes the same content without adding format, size, or truncation guidance, so baseline 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?

Opens with a specific verb and resource ('Audit an agent skill or instruction file') and immediately enumerates the concrete failure classes it detects: prompt-injection, guardrail-bypass phrasing, concealment instructions, exfiltration language, exposed credentials. It also names the sibling it is not (injection_scan), so the tool is distinguishable without opening any 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 an explicit trigger ('before trusting a skill or instruction file that came from outside your own repository') and an explicit exclusion with the correct alternative ('Not for arbitrary untrusted input at run time (injection_scan)'). The when/when-not/alternative triad is fully covered.

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