Get Credit Balance

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

The description clearly states a read-only action, consistent with the readOnlyHint annotation. It adds the context that the operation is specifically about credit balance, which is useful. Since the tool is trivial and non-destructive, no further behavioral disclosure is necessary.

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, concise sentence that directly conveys the purpose. There is no wasted verbiage, and it is front-loaded with the action and resource.

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?

Given the tool's simplicity (no parameters, read-only, no nested objects, no output schema), the description provides sufficient information. The agent can understand what the tool does and infer the return value (a balance amount). The readOnlyHint annotation covers safety, making the description complete for this trivial use case.

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 the description does not need to explain parameter semantics. The baseline for no parameters is 4, and there is nothing to add beyond the schema which is already empty and fully covered.

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 uses a clear verb 'Check' with a specific resource 'OpenRouter credit balance', which makes the tool's purpose immediately understandable. It does not explicitly differentiate itself from sibling tools like get_key_info or get_budget_status, but the resource name is distinct enough to avoid major 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?

The usage context is implied: use when you need to check the credit balance. However, the description does not provide explicit guidance on when to use this tool versus alternatives such as get_budget_status or get_key_info, nor does it state any exclusions or prerequisites.

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