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

Annotations (readOnlyHint=false, openWorldHint=true, idempotentHint=false, destructiveHint=false) only hint at the tool's nature. The description carries the full burden and delivers: it discloses the paid cost (0.002 USDC via x402 on Base), the two-step payment protocol, the 'Readiness evidence is not a safety guarantee' caveat, and the budget/policy constraint. 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?

Purpose is front-loaded and the description is logically structured (purpose → inspected fields → returns → usage guidance → payment flow). However, the [PAID:...] block is a dense run-on sentence mixing payment protocol, legacy argument support, and signing cautions; it could be tightened without losing content.

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?

For a complex paid tool with a two-step payment flow, an output schema, and policy constraints, the description is remarkably complete. It covers purpose, inputs, payment mechanism (both _meta and legacy _x402_payment paths), sequencing, budget/policy guardrails, and caveats. Nothing an agent needs to call it correctly is missing.

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 coverage is 100%, so baseline is 3. The description adds meaningful value beyond the schema: it explains the _x402_payment legacy base64 support, the two-step retry mechanism with _meta['x402/payment'], and ties max_usdc/agent_policy to the concrete policy (0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 and 0.002 USDC). This elevates it above the baseline.

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 a specific verb+resource: 'Live x402 endpoint readiness check before payment' – it probes and verifies an x402 paid API before an agent pays. It enumerates what it inspects (HTTP 402 challenge, payTo address, price, Base USDC network/asset, manifest freshness, buyer budget, spend policy) and what it returns (ALLOW/DENY, readiness score, report ID, settlement metadata, SHA-256 evidence receipt), distinguishing it from siblings like find_x402_tool and x402_readiness_verify as the paid pre-payment verification service.

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?

Provides explicit sequencing guidance: 'Run free can-pay and readiness checks first' and 'pay only when policy allows base 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 and 0.002 USDC is inside the agent budget.' It also names the two-step payment flow (call without payment, receive MCP PaymentRequired, retry with _meta['x402/payment']) and warns to 'Sign only after explicit budget and policy approval.' Nothing is left to inference.

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