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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false. The description adds valuable contextual information beyond these: it discloses cost ('Paid resource; x402 price is $0.002 USD per call') and the outcome structure ('returns blocking violations and warnings'). No contradiction with annotations; the added details enhance transparency, though it does not cover error behavior or rate limits.

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 three sentences, each with a distinct purpose: the first states the core function and result, the second scopes intended use and exclusions, and the third discloses cost. It is front-loaded with the most important information and contains no filler. This is an excellent model of conciseness.

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?

The tool has two required nested structures (facts and rules) and no output schema, yet the description provides no guidance on how to build these objects, what valid field/op combinations are, or what the response format looks like beyond 'blocking violations and warnings'. The description is too sparse for an agent to correctly invoke this tool without additional context, which is a significant gap given the schema's richness.

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% – the description does not mention parameter names or semantics. It only refers to 'caller-supplied facts' and 'explicit caller-supplied rules' without explaining their structure, the meaning of 'op' values, or how severities work. The schema itself provides detailed constraints, but the description fails to compensate for the total lack of parameter guidance, leaving an agent to infer how to construct valid inputs.

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 states a specific action and resource: 'Evaluates caller-supplied facts against explicit caller-supplied rules and returns blocking violations and warnings.' It also scopes the domain ('trust identity permission / trust unknown') and explicitly excludes legal/regulatory adjudication, which clearly differentiates it from many siblings. While it doesn't name a specific sibling, the purpose is unambiguous and specific.

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 provides explicit usage context ('Intended for trust identity permission / trust unknown') and a clear negative list ('Do not use for legal, identity, sanctions, fraud, contractual, or regulatory adjudication'). This gives an agent enough to decide when this tool is appropriate, though it does not directly compare against sibling preflight or policy-engine tools. Consequently, it stops short of a 5 but is well above minimal.

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