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

readOnlyHint=true already tells the agent this is a safe, non-mutating read, so the description's added value is limited to the underlying API route. It does not disclose pagination behavior, what a wallet object contains, or whether wallets can be empty/multi-currency. With annotations covering the safety profile, this is an adequate but not rich 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?

Two sentences, zero filler, and the core purpose is front-loaded before the endpoint detail. Nothing could be trimmed without losing 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?

There is no output schema, so the description carries some burden for describing what is returned, and it only names the entity type without saying what a wallet holds or that results are paginated. For a simple read-only list tool it is minimally sufficient, but it leaves the agent guessing about response shape.

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 100% and all three parameters (page, per_page, external_customer_id) are documented in the schema itself. The description adds no syntax, format, or constraint detail beyond the schema, so the baseline 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?

States a specific verb (List), a specific resource (prepaid credit wallets), and the scope (a customer's), which cleanly separates it from siblings like lago_list_customers or lago_list_customer_subscriptions. The API endpoint mapping (GET /customers/{external_customer_id}/wallets) reinforces exactly what is retrieved.

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 no when-to-use guidance, no prerequisites, and no alternatives. It never says to call this when you need a customer's balance or prepaid credits rather than, say, lago_get_customer or lago_get_customer_current_usage. The customer-scoped wording implies context but nothing is stated.

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