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

The description adds meaningful behavioral context beyond the annotations: 'Safe to call repeatedly; credits at most once' clarifies the idempotency and the side effect of crediting. This is consistent with idempotentHint=true and readOnlyHint=false, and no contradiction exists.

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 two short sentences with no filler. The core purpose is front-loaded, and the behavioral note about repeated calls 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 status check with an output schema, the description plus annotations cover the essential behavior and side effects. It could be slightly richer by explicitly naming create_card_topup as the source of sessionId or distinguishing verify_payment, but nothing critical is missing.

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?

Both parameters are fully documented in the schema, including format hints (cv_live_…/cv_test_… and cs_…). The description itself adds no additional parameter-level meaning, so the baseline of 3 applies.

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 a specific action ('check') on a specific resource ('card top-up session') and defines the outcome ('paid and credited'). It is distinguishable from create_card_topup by direction, though it does not explicitly differentiate itself from the similarly named verify_payment sibling.

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 conveys the condition it answers and notes that repeated calls are safe, which implies a polling/status-check use case. However, it never names alternatives such as verify_payment or get_ledger, nor does it state when not to use this tool, leaving the agent to infer routing among siblings.

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