Get credit balance and costs

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

Annotations already provide readOnlyHint=true, and the description adds important context beyond that: the call itself 'Costs no credits,' the data is for the 'authenticated user,' and the costs are 'live.' This helps the agent set user expectations without overexplaining.

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 short sentences with no filler: the first states the core return value, the second explains when to call it, and the third notes it is free. The most important behavioral facts are front-loaded and every sentence earns its place.

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 parameters, read-only annotations, and no output schema, the description supplies all essential context: what is returned, the cost categories, the recommended call timing, the stop-early policy, and the fact that the call itself is free. Nothing critical is missing for an agent to invoke 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, so there is nothing for the description to clarify about arguments. The baseline of 4 applies because no parameter semantics are needed, and the description still explains what the returned information represents.

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 opens with a clear verb and resource: 'Return the authenticated user's credit balance and the live per-action credit costs.' It lists the specific cost categories, making the tool's scope unambiguous and distinct from all sibling generation and retrieval tools.

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 explicitly tells the agent when to call this tool: 'Call it before any generation tool so you can tell the user the cost and stop early when the balance is too low.' It also gives a deterministic rule for cost-aware behavior and notes the CLI equivalent, leaving no ambiguity about its role.

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