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

Annotations declare readOnlyHint=true and openWorldHint=true, and the description adds substantial beyond-annotation context: the $0.20 USDC/x402 price, the PaymentRequired challenge on unpaid calls, and the exact retry mechanism via _meta['x402/payment']. This is exactly the auth/payment behavior an agent needs to invoke the tool successfully.

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?

Three sentences, purpose front-loaded ahead of the payment mechanics. Every sentence earns its place, though the payment detail adds length that is justified only because the x402 flow is non-obvious.

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?

With no output schema, the description usefully states what is returned (risk-tier delta plus per-vendor summaries) and fully covers the payment/auth flow. For a two-required-parameter read tool it is essentially complete, with only return-format detail (structure of the delta) left unspecified.

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 all four parameters (including the optional product_current/product_proposed) are already documented in the schema. The description adds no parameter-level meaning beyond what the schema provides, so the 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 ('counterfactual vendor-swap risk comparison') and clarifies scope by naming the underlying assessment '/ot/vendor-risk' as the per-vendor engine. It also names the sibling getVendorRisk implicitly, letting an agent distinguish the delta-comparison tool from the single-vendor tool 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?

Gives a clear usage context ('for pre-purchase or migration decisions') and frames itself as counterfactual comparison versus a single assessment. It does not explicitly name getVendorRisk as the alternative to use for a single-vendor lookup, so the routing guidance is clear but not fully enumerated.

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