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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds genuinely new context beyond them: the auth requirement (signed-in user or API key) and that the call is 'free' – i.e. consumes no credits, which is non-obvious and relevant on a credit-centric API.

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?

Three tight sentences with the purpose front-loaded, then prerequisites, then the read-only/free note. Each sentence earns its place, though the auth sentence is slightly wordy.

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 zero-param, no-output-schema tool, the description covers what it returns ('remaining credits'), the auth prerequisites, and the cost profile. Only the concrete return shape (numeric balance vs. a structure) is left implicit, a minor gap.

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?

There are zero parameters, so by the stated rule the baseline is 4. The description correctly does not invent parameter details, and nothing about parameter meaning is missing.

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 ('Returns the remaining credits') and scopes it precisely to 'the user's own Wozapi account', which distinguishes it from siblings dealing with payments, prices, addresses, or trials. An agent knows immediately this is the balance-read tool.

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?

It gives clear context for when the tool is callable and what happens when prerequisites are unmet ('when neither is there, the client asks the user to sign in first'). It doesn't name alternative tools, but no sibling overlaps in function, so there is little to disambiguate.

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