pay_url

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

Adds significant detail beyond annotations: payment challenge auto-satisfaction, default payment ceiling, allowance wallet usage, idempotency key forwarding, and response contents (HTTP response + receipt).

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?

Single focused paragraph, front-loaded with core action, no redundant phrasing. Every sentence adds relevant 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?

Covers purpose, payment mechanism, idempotency, return value. Lacks detail on error scenarios or behavior when URL does not support x402. Otherwise complete for a tool with no output schema.

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 covers all parameters with descriptions (100% coverage), so baseline applies. Description reinforces defaults (e.g., $0.10 ceiling) and idempotency behavior but does not add new meaning beyond schema.

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?

Description clearly states it calls an HTTP URL with automatic payment challenge satisfaction, distinguishing it from siblings focused on other operations. It specifies the action, resource, and unique capability.

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 context like default ceiling, allowance wallet, and idempotency key forwarding but lacks explicit guidance on when to use vs alternatives or when not to use.

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