x402_estimate_cost

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It explicitly states the most critical behavior: the tool does not make a payment, indicating a non-mutating, read-only operation. This is valuable context that prevents misuse. However, it does not disclose whether the tool makes a network call to the endpoint, returns a cached value, or requires any authentication, leaving some behavioral detail unspecified.

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 a single, concise sentence that front-loads the action ('Estimate') and includes a key qualifier ('without making a payment'). Every word earns its place, and there is no redundancy or irrelevant detail.

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 simple tool with one parameter, no output schema, and no annotations, the description is reasonably complete. It clearly conveys the purpose and the non-payment behavior, which is the core concern. However, because there is no output schema, the description could have briefly indicated what the returned estimate includes (e.g., currency, fees), but this is a minor gap given the tool's simplicity and the presence of sibling tools that may carry that context.

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?

The input schema has 100% description coverage for the single 'url' parameter ('The URL to check for payment requirements'), so the schema already provides sufficient meaning. The tool description adds no additional parameter semantics beyond what the schema includes, which aligns with the baseline of 3 for high schema coverage.

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 description clearly states the tool's purpose: 'Estimate the payment cost for an x402-protected endpoint without making a payment.' It uses a specific verb ('estimate'), identifies the resource (payment cost for an x402-protected endpoint), and distinguishes itself from payment-execution tools by explicitly noting it does not make a payment. This effectively differentiates it from siblings like x402_pay_request and x402_send.

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?

The description provides clear context for when to use this tool: when you need to know the payment cost before actually paying. However, it does not explicitly mention alternatives or give exclusions, such as noting that this should be used instead of x402_estimate if that is a different variant. The guidance is clear but lacks explicit sibling differentiation.

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