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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds the notable behavioral/pricing context of a paid tool (5 prepaid credits, production billing required), which matters for invocation decisions. It does not disclose output shape or ordering, but read-only plus cost disclosure is reasonable above the annotation 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?

Two short sentences with no filler, and the functional statement comes first. The billing notice is set off clearly but is somewhat terse, reading more like a warning tag than integrated guidance.

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 read-only two-array comparison with no output schema, the definition conveys purpose, safe-read semantics, and cost. The main remaining gaps, exact output format and element type expectations, are modest given the tool's simplicity.

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?

Only two parameters with 0% schema description coverage, so the description must carry meaning, and it does: it clarifies that 'requested' is the candidate privilege set and 'allowed' is the least-privilege policy they are compared against. It does not specify item format (strings vs objects) or nesting, leaving some ambiguity. With just 2 params and the comparison semantics explained, a 4 is fitting.

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+resource: identify requested privileges absent from an allowed policy. That is a clear set-difference operation distinguishable from a generic scope check, though it does not explicitly name the sibling privi_scope_check as the alternative.

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?

No when-to-use or when-not-to-use guidance beyond the implicit framing that you need both a requested set and an allowed policy. No prerequisites or alternatives named, so the agent must infer routing between this and privi_scope_check.

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