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

Discloses cost ($0.003) and behavior (decoding, reporting, verifying). No annotations provided, so description fully carries the burden. No contradictions, clear about what the tool does.

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, front-loaded with key action, zero waste. Every phrase adds value.

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 tool with 2 params, no output schema, and no nested objects, the description fully explains purpose, usage, cost, and provides sibling differentiation. No gaps identified.

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 covers both parameters fully (100% coverage). Description adds context about the 'address' parameter's role in Base affordability verification, going beyond schema descriptions. Minor improvement, hence 4.

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?

Specific verb 'Pre-flight' with clear resource (payment endpoint) and actions (decode challenge, report costs, verify affordability). Distinguishes from sibling tool x402_inspect.

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?

Explicitly states when to use ('before paying an unfamiliar endpoint') and when not to ('use x402_inspect to lint an endpoint you own'), providing a direct alternative.

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