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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world). The description adds genuinely new behavioral context: no private keys are received, the selection is deterministic and signed, and there is a cost ('0.003 USDC'). However, that cost string is ambiguous (invocation fee vs. payment amount) and 'evidence-bounded' is unexplained jargon.

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 core clause is followed by a stray semicolon and a string of unparsed fragments ('0.003 USDC. Deterministic, evidence-bounded and signed.') that read as boilerplate rather than front-loaded, actionable 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?

An output schema exists so return values need not be explained, but with zero declared parameters and an example-only schema, the description should clarify what inputs to supply and what 'exact compatibility' means. It does neither, leaving a critical gap for an agent trying to invoke it.

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?

Parameter count is 0, which normally earns a 4 baseline, but the schema declares no properties at all while its example reveals client_capabilities and payment_requirements inputs that the description never mentions. The description therefore fails to compensate for a schema that documents inputs only by example.

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 verb 'Select' plus resource 'x402 v2 payment requirement' gives a workable gist, but 'exactly compatible' is undefined and the description never says with what the requirement must be compatible or where candidates come from. Siblings like x402_quote_comparator, payment_route_selector, and payment_preflight occupy nearly identical semantic ground with no differentiation.

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?

There is no when-to-use, when-not-to-use, or prerequisite guidance. Given a sibling list dense with routing/selection tools (payment_route_selector, x402_quote_comparator, payment_preflight), the absence of any routing cue leaves the agent guessing which tool to call.

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