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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so 'read-only, deterministic' is largely redundant. The one genuinely additive fact is the cost ('0.002 USDC'), which annotations do not convey. It says nothing about what makes a route 'impossible,' error behavior, or the decision criteria, so beyond the price disclosure it adds little for a mutation-free tool.

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?

A single, dense, front-loaded sentence with the operative verbs first and the cost/behavior facts after a semicolon. Every clause carries information, though the triple-verb construction ('reject/rank/return') packs distinct behaviors tightly.

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?

An output schema exists, so return values need no exposition, and annotations carry the safety profile. But for a tool taking two complex nested-object parameters at 0% schema coverage, the description omits any parameter semantics, usage context, or explanation of the 'impossible vs safe eligible' decision rules that are the tool's core behavior.

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 both required parameters are nested objects with many sub-fields (route eligibility flags, policy constraints). The description references 'policy' only obliquely and never explains any field like allowed_networks, max_latency_ms, or the route eligibility flags, so it fails to compensate for the coverage gap.

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 specific verbs and resource: 'reject impossible x402 routes, rank safe eligible routes by policy and return the exact next payment action.' An agent can infer this is a deterministic route-selection/filter step in the payment pipeline. It does not, however, explicitly differentiate itself from close siblings like x402_v2_router or x402_quote_comparator, so it falls short of a 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?

No when-to-use, when-not-to-use, or alternative routing is given. With siblings such as x402_v2_router, payment_preflight, and x402_quote_comparator, the agent has no stated signal for choosing this tool over them, nor any prerequisites or ordering guidance.

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