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

With no annotations provided, the description carries full responsibility for behavioral disclosure. It only says 'returns' a balance, which implies read-only behavior but doesn't explicitly state safety, auth requirements, or potential side effects. The description also omits details on error conditions or response handling beyond mentioning a 'values' object, leaving significant gaps.

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 main description is concise, front-loading the purpose and adding domain context in a short paragraph. The @param and @return lines are appended in JSDoc style, which is somewhat unconventional but keeps info compact. It is not bloated, though minor formatting issues ('json object,in') reduce polish.

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?

Given the tool's low complexity and the presence of an output schema, the description is adequate but not fully complete. It doesn't clarify the currency scope or whether the balance is per-currency or total, and terms like 'fup units' aren't expanded. The existence of an output schema reduces the need for return-value details, but there are still contextual gaps.

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 schema provides only the type and requirement for customer_id, with zero description coverage. The description adds the meaning 'The customer's database id', which helps but doesn't explain how to obtain or use it. This minimal addition gives some value but is not thorough enough for a higher score.

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 'Returns the customer's credit balance in currency' with a specific verb and resource. It also provides context on how credit balances arise (overpayment or voucher redemption), which helps differentiate it from similar balance-querying siblings. However, it doesn't explicitly name alternatives or contrast with other getter tools, so it falls short of a 5.

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 implies the tool is used to retrieve a customer's credit balance, and the background explanation suggests typical scenarios. However, it provides no explicit guidance on when to prefer this tool over alternatives, nor any exclusions or prerequisites. Usage is implied rather than directly stated.

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