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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the agent knows it is a safe, non-mutating operation. The description adds the pricing information ($0.002 per call) and clarifies the return type (blocking violations and warnings), which supplements the annotations with useful context. It doesn't detail error behavior or edge cases, but the annotations cover the key safety traits.

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?

The description is concise, with three sentences: one for core functionality, one for usage exclusions, and one for pricing. The most critical information (evaluates facts and rules) is front-loaded. It wastes no words, though the pricing sentence could be seen as auxiliary.

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 rule-evaluation tool with nested objects and no output schema, more could be done to clarify what 'facts' means structurally and the exact output format. The exclusions and pricing are helpful, and the schema provides some rule structure, but the facts parameter remains opaque Von an agent's perspective, leaving some ambiguity in how to construct valid input.

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%, so the description must compensate for the lack of parameter documentation. The description only says 'facts' and 'rules' without detailing their structure or semantics; the schema defines rules as an array with fields like op, field, value, but the description leaves the facts object entirely undetermined. This is minimal compensation for two complex parameters.

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?

The description clearly states the tool evaluates caller-supplied facts against caller-supplied rules and returns blocking violations and warnings, which is a specific verb-resource-action combination. It further distinguishes its intended use for execution safety and explicitly excludes other domains like legal, identity, sanctions, etc., differentiating it from potentially similar policy engines.

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?

The description explicitly states that the tool is intended for execution safety and should NOT be used for legal, identity, sanctions, fraud, contractual, or regulatory adjudication, providing clear when-not-to-use guidance. However, it does not explicitly name alternative tools for those other domains, so it stops short of a full 5.

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