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

Annotations already establish read-only, idempotent, non-destructive behavior; the description adds complementary context by disclosing that the resource is paid at a specific x402 price and that evaluation is limited to caller-supplied facts/rules, plus the output categories of blocking violations and warnings. No contradiction with annotations.

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?

Three sentences, each earning its place: purpose, applicability/exclusions, and cost. The main behavior is front-loaded and no information is repeated from the schema or annotations.

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 generic rule-evaluation tool, the description covers domain, exclusions, and return categories, and robust annotations cover safety traits. However, with no output schema and zero parameter documentation, the agent is left without guidance on facts structure, rule composition beyond the schema, or the exact shape/order of returned violations and warnings.

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%, and the description only says facts and rules are caller-supplied; it does not explain how to shape the facts object, how field paths are resolved, or how severity maps to output. The rule schema is self-explanatory, but the opaque facts parameter is not compensated for in prose.

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 opens with a specific action and resource: 'Evaluates caller-supplied facts against explicit caller-supplied rules and returns blocking violations and warnings.' It further distinguishes this engine from its many policy-engine siblings by scoping it to 'agent procurement / trust unknown' and explicitly excluding legal, identity, sanctions, fraud, contractual, and regulatory adjudication.

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 clearly states the intended context ('agent procurement / trust unknown') and gives a strong when-not-to-use list ('Do not use for legal, identity, sanctions, fraud, contractual, or regulatory adjudication'). It stops short of naming a specific sibling tool as the alternative, so it falls just below full explicit routing.

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