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

With no annotations, the description must carry behavioral burden. It usefully clarifies that buy_100_credits only *generates a Checkout URL* rather than charging the account directly, and distinguishes free daily quota from permanent paid credits. It omits permission/auth requirements, whether the URL expires or is single-use, pricing beyond the HK$ 100 figure, and any side effects of the top-up.

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?

A single well-formed sentence covering both branches, front-loaded with the more common inspection action before the purchase action. Every clause carries information and there is no filler, though the two-branch structure packed into one sentence is slightly dense.

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 and no annotations, so the description is the only source of behavioral and return information. It conveys what balance the check reports and that the buy branch yields a Stripe URL, but it does not describe the shape of the returned balance (free vs paid breakdown, reset timing) or what the caller should do with the URL. Adequate but with clear gaps for a tool with zero structured support.

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 the single enum parameter is fully documented with both values explained in the schema itself. The description largely restates the same two actions, adding no syntax or format detail beyond the schema. Baseline 3 is appropriate when the schema does the heavy lifting.

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 states two concrete capabilities with specific resources: checking remaining free daily quota and paid credit balance, and generating a HK$ 100 Stripe Checkout URL for 100 permanent credits. The verb+resource pairing is clear and the two modes are distinguishable. It does not differentiate from siblings, but the sibling list (company search/filing tools) is unrelated, so there is little risk of confusion.

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?

Usage is implied by the two-branch phrasing: check when you need balance visibility, buy when you want to top up. However, there is no explicit when-to-use guidance, no exclusions, and no statement of prerequisites (e.g., whether a paid account is required to buy). The default of check_balance is only communicated via the schema, not the description.

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