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

No annotations are provided, so the description carries the burden. It explicitly states 'Read-only, spends nothing' which is a key behavioral trait. It also notes the requirement for a valid api_key. It does not mention error handling or rate limits, but for a simple read operation this is adequate. It discloses the return fields (balance, level, discount) which adds context.

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 front-loaded with the core purpose, then provides usage guidance and alternatives. It includes a redundant Vietnamese translation, but it does not add much bulk. Overall it is well-structured and every section serves a purpose.

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 single-parameter tool with no output schema, the description covers what it returns (balance, level, discount), when to use it, and what alternatives exist. An agent has everything needed to invoke it correctly. The Vietnamese translation also aids non-English users.

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% and the api_key parameter is fully described in the schema, including its source ('Trang cá nhân → API'). The description only repeats that it requires the api_key, adding no new semantics beyond the schema. Baseline 3 is appropriate given the high coverage.

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 verb and resource: 'Get your account balance, level and discount' and explicitly differentiates from siblings by naming wallet_history, topup_guide, and quote_order as alternatives. This makes it unambiguous which tool to pick for balance queries.

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?

Provides explicit 'WHEN TO USE' conditions (user asks 'how much do I have' or needs to confirm funds before quote_order/buy_product) and 'PREFER INSTEAD' guidance for alternative tools, covering both when to use and when not to use.

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