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

Annotations already declare this is a non-read-only, non-destructive, non-idempotent mutation. The description adds genuinely useful context that creating an order is not the same as crediting the balance — you must pay it — but says nothing about idempotency_key behavior, order expiry, or whether an order ID is returned for the follow-up pay step.

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?

One short sentence, front-loaded with the verb and resource, with the amount constraint in parentheses so nothing is buried. It is efficient, though arguably terse to the point that key behavioral detail is omitted.

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 4-parameter mutation with no output schema, the definition covers the amount bound and the payment follow-up, but omits what an agent needs to close the loop: whether the response contains an order identifier to pass to pay_order, and whether repeated calls with the same idempotency_key are deduplicated.

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 50%: chain and token carry rich descriptions (defaults, chain IDs, decimals), while amount_usd and idempotency_key have none. The description usefully supplies the missing amount range (5–5000), but leaves idempotency_key semantically undefined in both places.

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?

States a specific verb and resource ("Create a top-up order") and adds a concrete amount band (USD 5–5000), which separates it from the domain-order siblings like create_order. It does not explicitly name the sibling it complements, but the purpose is unambiguous.

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?

"pay it like any order" implies the create-then-pay two-step flow and effectively points at pay_order, but no tool is named and there is no statement of when to use this versus buy_with_balance or create_order. Usage is implied rather than spelled out.

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