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

Beyond the annotations, the description clearly explains the two-mode behavior: quote-first with a 402 challenge plus retry details, or direct credited response when an MPP runtime wraps the fetch. The destructiveHint=true annotation is surprising for a top-up, but the description's mention of completing a purchase is consistent with side-effecting financial behavior, not a contradiction.

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 compact and front-loaded with the purpose and trigger condition. Every sentence contributes essential behavioral or routing information, with no repetition or 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 financial side-effecting tool with output schema, annotations, and full parameter documentation, the description covers the trigger, workflow, and conditional behavior sufficiently. Nothing critical is missing for an agent to decide whether and how to invoke it.

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 parameter details are already fully documented. The description does not add additional meaning about credits or dry_run beyond what the schema provides, making the baseline score of 3 appropriate.

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 states a clear verb and resource: prepare or complete a MyOTP credit purchase using USDC/card through MPP. It also differentiates itself from siblings by describing both the quoting and payment-completion workflow, making it distinct from get_topup_quote.

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 gives a concrete trigger: use when generate_otp or another send fails with HTTP 403 insufficient balance / NoBalance. It does not explicitly name alternatives or state when not to use this tool, but the triggering condition is clear and actionable.

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