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

Annotations only declare readOnlyHint and openWorldHint. The description adds critical context beyond them: the preview NEVER charges, it WITHHOLDS the provider URL and ready-to-pay x402 challenge, it returns the pick + survivor count to prove a live provider, and the paid sibling returns PaymentRequired on an unpaid call. That is exactly the behavior an agent needs to avoid botching a paid flow.

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?

Front-loads purpose in the first clause and orders content logically (what it does → what it returns/withholds → alternative → when to use). Some marketing phrasing ('Buyer-side trust oracle', quoted intent) adds length but each sentence still carries routing or behavioral 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?

No output schema exists, yet the description explicitly enumerates the return payload (vetted pick name, usage stats, reason, survivor count) and what is withheld. For a preview tool with a paid sibling, 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 description coverage is 100% and all three parameters (need, chain, budget_usd) are already documented with examples and defaults in the schema. The description adds the budget-gating concept but no syntax or format detail beyond what the schema provides, so baseline 3 applies.

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 (a free PREVIEW that vets and ranks x402 providers from Coinbase Bazaar) and explicitly names the sibling it is not (verified_route, the paid full sweep). An agent can distinguish preview from paid variant without opening either schema.

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 an explicit 'Use when' list of triggering intents ("which x402 tool for X", "avoid a scam/dead stub", "vet before I pay") and names the alternative (verified_route / agentpay-x402 SDK) with the exact price and condition that selects it.

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