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

With annotations only covering read-only and open-world behavior, the description adds substantial context: $0.01 USDC per call, failed calls cost nothing, quote-first payment flow, ranking by paying wallets and repeat buyers, cautions, and Tollkit's own-seller disclosure. It also explains why raw call counts are avoided.

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 definition is front-loaded with purpose and then uses labeled sections for pricing, when-to-use, alternatives, parameters, and returns. Every sentence carries useful information, and none are filler.

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?

Although there is no output schema, the description explains the return shape: ranked endpoints, one per seller, with price, paying wallets, repeat buyers, and cautions. Combined with annotations covering safety and open-world scope, the definition is complete enough for an agent to invoke it correctly.

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 100%, so task, limit, and payment are already fully documented, including the 1-20 range/default and the quote-mechanism for payment. The description repeats the schema's parameter guidance but does not add parameter-specific syntax or constraints beyond what the input schema already provides.

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 first sentence states a specific verb and resource: 'Find the best paid x402 API for a task.' It then distinguishes the ranking methodology from siblings and names two alternatives, so an agent can tell it apart without opening schemas.

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?

It gives an explicit 'When to use' condition and a 'Use instead' section naming find_service and x402_seller_lookup with their respective scopes. It also explains the quote flow for payment, leaving no ambiguity about when to call with or without payment.

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