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

Annotations already say readOnly/idempotent/non-destructive, so the description does not need to repeat safety. It adds behavior not in the annotations: the tool ranks but cannot select, and it is a paid resource with a fixed x402 price.

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?

Four short sentences with no filler: function, intended scope, exclusions, and pricing. The main action is front-loaded and every sentence adds new information.

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 no output schema and moderate input complexity (nested candidates, optional weights/constraints), yet the description does not specify return shape, ordering direction, or scoring behavior. It covers purpose, exclusions, and cost, but an agent must infer the remaining operational details from field names.

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 has to explain parameters. It gestures at the three groups (candidates, constraints, weights) and the ranking dimensions, but does not explain normalization, default weight behavior, or how constraints filter candidates; the schema field names must carry that weight.

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 first sentence names a specific action ('ranks'), the resource ('caller-supplied candidates'), and the signal list (price, reliability, latency, trust, quality), so an agent can tell what it does. It stops short of naming an alternative or differentiating itself from the many other selection_routing_router_* siblings, so it is not a full 5.

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?

'Intended for selection routing' gives positive context and 'Do not use for legal, identity, sanctions, fraud, contractual, or regulatory adjudication' gives explicit exclusions. No alternative tool or fallback is named, but the boundary is clear.

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