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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the agent knows this is a pure, side-effect-free computation. The description adds genuinely new context the annotations do not carry — a paid, credit-metered billing precondition — but says nothing about input expectations, error behavior when arrays are malformed, or what the result contains.

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?

Two short sentences with the core action front-loaded and the billing constraint second. Nothing is redundant, though the paid notice is delivered as a terse code phrase rather than as a usable precondition.

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 two undocumented required array parameters, no output schema, and no annotations covering semantics, the description is too thin for the tool's ambiguity. An agent cannot tell what to put in the arrays or what it will get back, so the definition is not complete enough to invoke confidently.

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 description coverage is 0%: both required arrays are typed only as "array" with no item schema. The description implies the semantics ("required" = required control set, "evidenced" = controls with evidence), but it never states element shape, identifier format, whether duplicates matter, or how matching is performed — the critical detail for a set-difference operation.

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?

"Calculate which required policy controls have no evidence" gives a specific action (set difference over required vs. evidenced controls) on a specific resource. It is clear enough to act on, but it never distinguishes itself from the similarly named sibling privi_pro_control_evidence_gap, leaving overlap unresolved.

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?

There is no when-to-use or when-not-to-use statement and no named alternative among the many siblings. The only situational information is a billing precondition ("PAID ONLY: 5 prepaid credits"), which is a gate rather than guidance on when this computation is the right choice.

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