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

With no annotations provided, the description carries the full burden. It clearly states that no money moves immediately—only a URL is returned, and balance credits occur upon payment. It also notes that the call is free and requires specific auth keys, providing good behavioral disclosure.

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, well-structured paragraph of about 4 sentences. It front-loads the main purpose, then clarifies behavioral nuances, usage context, auth, and an example. No redundant 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?

For a tool with 3 parameters and no output schema, the description explains the core purpose and outcome (returns a URL), auth, and an example. However, it omits documentation for the two optional parameters (cancelUrl, successUrl), which are important for the agent to use the tool effectively.

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 3 parameters but only 'amountUsd' is described in the description ('dollars (whole cents)'). The optional 'cancelUrl' and 'successUrl' are not mentioned. With 0% schema description coverage, the description should compensate, but it leaves two parameters undocumented.

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 creates a one-tap Stripe Checkout link to add credit to the user's balance. It uses a specific verb 'create' and resource 'topup link', distinguishing it from sibling tools like 'create_baton' or 'create_contract' which serve different purposes.

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 context: use when balance is insufficient, and notes that the link is handed to a human for payment. It mentions auth requirements (rs_live_* key) and that it's not for x402 callers. However, it does not explicitly state when not to use the tool or mention alternative tools.

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