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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds meaningful behavioral context beyond annotations: monthly credits reset each period, pack credits never expire, and audits spend credits pay-as-you-go. This helps the agent interpret the returned balance correctly.

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 and credit types, then moves into usage context and pricing. The pricing and upgrade URL details, while relevant to credit management, go beyond what is needed for tool selection and invocation, making the description somewhat longer than necessary.

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-parameter, read-only balance tool, the description covers the essential return semantics (monthly vs. pack credits), the audit cost model, and the minimum balance required to start an audit. It is sufficiently complete for an agent to know what to expect and when to call it, even without an output schema.

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, so there is nothing for the description to add beyond what the schema already conveys. With 100% schema coverage and no parameters to document, the baseline of 4 applies.

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 identifies the tool's purpose: retrieving the organization's credit balance. It names the specific resource ('credit balance') and distinguishes the two components (monthly credits and pack credits), making it easy for an agent to understand what this tool returns and how it differs from credit-related siblings like list_credit_transactions.

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 provides strong contextual guidance by explaining how audits consume credits, noting that run_audit shows an upper-bound estimate, and establishing the 50-credit minimum threshold for starting an audit. It does not explicitly name alternative tools or state when not to use this one, but the context clearly implies this should be checked before running audits.

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