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

With no annotations, the description carries the full burden for behavioral disclosure. It covers credential requirements and the need for a prior payment payload, but it does not mention the resulting side effect (credit balance increase) or possible return/error 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 exactly two sentences, front-loaded with the primary action and followed by necessary credential context. Every sentence contributes meaningful information with 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?

The workflow and authentication prerequisites are well covered, but with no output schema and no annotations, the description leaves return values and error cases unspecified. For a paid top-up tool in a multi-step flow, additional completion details would make it more robust.

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%, but the description adds value by clarifying the either/or relationship between apiKey and accessToken, and by explaining that paymentPayload is the payload from a prior payment step. This goes beyond the schema's individual field descriptions.

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 'Complete an endpoint credit top-up' with a specific verb, resource, and phase. It distinguishes itself from the sibling request_endpoint_topup_payment by emphasizing the completion step after obtaining a payment payload.

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 temporal context ('after you have obtained a valid X-Payment payload') and specifies accepted credential types. It implies the preceding payment request step without explicitly naming the sibling tool, so it is clear but not fully exhaustive.

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