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

With no annotations, the description carries the burden of behavioral disclosure. It discloses the primary output (Stripe Checkout URL) and the sandbox override, but does not mention potential side effects (e.g., does it create a pending charge?), idempotency, or error handling. The information provided is useful but incomplete for a payment tool.

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?

Two sentences with no filler. The main purpose is front-loaded, and the sandbox caveat is appended concisely. Every word earns its place.

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 two-parameter tool with no output schema, the description covers the return value and sandbox behavior. It does not mention failure modes, idempotency, or whether the payment link expires, but these are likely not critical for basic usage. Overall, it is adequately complete for the tool's complexity.

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 description coverage is 50% (api_key has a description, amount_usd does not). The tool description adds no parameter-specific details. amount_usd is self-explanatory as a dollar amount, and api_key's schema description already covers authentication. Baseline 3 is appropriate since the description does not compensate for the missing amount_usd description but does not need to.

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 uses a specific verb 'Create' with a clear resource 'a payment link to add credits' and explicitly states the return type (Stripe Checkout URL). It is distinct from all sibling tools, none of which handle top-ups, so an agent can easily identify its purpose.

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 context is clear: use when you need to add credits via a payment link. It also notes sandbox-mode behavior. However, it does not explicitly state when not to use or mention alternatives, though none exist among siblings, so this is a minor gap.

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