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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the description need not repeat those. It adds the API key requirement and specifies the output contents (credit balance, available hours, pricing), which provides useful behavioral context beyond the annotations. It does not describe error handling or response format, but the added info is meaningful.

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 a single, efficient sentence. The core action and data ('balance, available hours, and pricing') are front-loaded, followed by the prerequisite. There is no redundant wording or unnecessary explanation.

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?

With no output schema, the description adequately conveys what the tool returns (credit balance, available hours, pricing) and the required authentication key. It does not mention units, error conditions, or usage limits, but for a simple read-only tool with no inputs, this is sufficiently complete for an agent to call it correctly.

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 tool has zero parameters, and the input schema is empty. Per the baseline for 0 parameters, a score of 4 is appropriate since the description doesn't need to explain any parameters. It correctly omits parameter details and still informs the agent of the data returned.

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 action 'check' and the exact resources: credit balance, available hours, and pricing. This distinguishes it from siblings like get_pricing (which may only cover pricing) and get_billing_history (history of transactions), so an agent can identify the specific purpose without ambiguity.

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?

No guidance is provided on when to use this tool versus alternatives such as get_pricing or get_account. The only mention is 'Requires a configured API key', which is a prerequisite, not a usage guideline. There are no exclusions or references to alternative tools, leaving the agent to infer the appropriate context.

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