x402_pay

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

No annotations are provided, so the description carries full responsibility, and it delivers: it discloses that money is spent from the agent's balance/credit, that spend limits/budgets/allowlist apply, that a settled receipt is returned, and that idempotency prevents double payment. It also notes that payment/framing headers are stripped server-side, which is important non-obvious behavior.

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 well-structured and front-loaded with the core action, followed by payment/return details, then tactical guidance and prerequisites. It is slightly dense but every sentence serves a distinct purpose: what it does, how to use it safely, what to do first, and what credential is needed. No 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?

For a complex, money-moving tool with no annotations and no output schema, the description is remarkably complete. It covers the payment mechanism, constraints, idempotency, prerequisites, return content (vendor response plus X-Floe-* metering headers), and directs users to estimation tools first. This is sufficient for an agent to safely invoke the tool.

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%, so the baseline is 3. The description adds genuine value beyond the schema by explaining the purpose of idempotency_key ('so retries never double-pay') and clarifying that headers are stripped of payment/framing headers. The body parameter's note to JSON-encode yourself is also reinforced contextually.

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 opens with a specific verb and resource: 'Execute a paid x402 call through the Floe proxy.' It clearly distinguishes this payment-execution tool from sibling estimate/check tools by stating that Floe pays the vendor in USDC and returns metering headers. It also explicitly directs users to estimate_x402_cost or x402_forecast first, reinforcing its unique role.

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 explicit guidance: 'Use estimate_x402_cost or x402_forecast FIRST' and 'Pass idempotency_key (Stripe-style) so retries never double-pay.' It also states a hard prerequisite ('Requires an agent key (floe_...)') and mentions spend limits, budgets, and allowlist constraints, giving clear when-to-use and when-not-to-use context.

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