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

Annotations already declare non-read-only, open-world, non-idempotent, non-destructive behavior. The description adds valuable context: it returns payment requirements in USDC on Base, does not perform payment, and requires a signed PAYMENT-SIGNATURE header to proceed. It does not explain whether the call creates or reserves an order, so it is not fully transparent about write-side effects.

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 description is short and front-loaded with purpose, followed by the non-payment behavior and next-step workflow. Every sentence contributes useful 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?

With no output schema, the description still explains the return type, currency/network, amount inclusion, and the key pay_url field. It is sufficient to call and proceed, though it could enumerate the full response shape or clarify order creation side effects.

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%, and each parameter already has a description. The description adds only that idx is zero-based and ties the parameters to check_coverage results, so it adds some meaning but mostly restates structured information.

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 action: selecting one check_coverage candidate and returning x402 payment requirements. It clearly distinguishes the tool from check_coverage and get_report by describing its role in the workflow.

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 says the tool does not pay, then explains the next step: send the signed payment in a PAYMENT-SIGNATURE header to the returned pay_url, then use get_report. This gives both when to use it and how it relates to alternatives.

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