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

Annotations already convey readOnly, idempotent, and non-destructive traits. The description adds useful context: the decision is 'free' and the 'free result is sufficient by default,' which clarifies the behavior around require_audit_receipt. 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?

Two sentences, no fluff. The first sentence states the core purpose, and the second gives crucial conditional advice. Every word earns its place.

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?

Given the tool's moderate complexity, the description covers its purpose, key policy options, and the conditional flag. It does not elaborate on endpoint or max_usdc, but the output schema exists and annotations handle safety, so the description is sufficiently complete for a preflight decision tool.

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 low (25%), so the description carries more responsibility. It explains agent_policy (strict/standard/permissive) and offers guidance on require_audit_receipt, but leaves endpoint and max_usdc without added meaning beyond the schema's bare type declarations.

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 clearly states a specific action: 'Agents ask whether an x402 endpoint should be paid under strict, standard, or permissive policy.' This includes a verb, resource, and distinct scope (payment policy), effectively distinguishing it from sibling tools like x402_readiness_verify or find_x402_tool.

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 clear usage context: it's a pre-payment policy decision, and it advises when to set require_audit_receipt ('only when a settlement-backed receipt is required'). However, it does not explicitly name alternatives or state when not to use this tool, so it misses the top score.

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