Get usage

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

Annotations already declare readOnlyHint=true, so safety is known. The description adds behavioral detail about the returned content (spend by meter, by agent, recent runs) and its semantic role ('where credits went'), which goes beyond the annotation. No contradictions.

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?

Two sentences with zero filler. The first sentence states the action and scope; the second provides use-case guidance and an explicit alternative. Perfectly front-loaded and concise.

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 no-parameter, read-only tool with strong annotations, the description is complete: it explains the return content, the intended use case, and disambiguates from get_credits. No output schema exists, so the description carries the full explanatory burden, and it succeeds.

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 description does not need to elaborate on parameter semantics. Baseline for 0 params is 4; the description adds meaning about what the rollup contains without needing parameter detail.

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 a specific verb ('Get'), a resource ('usage rollup'), and details what it includes ('spend by meter and by agent, recent runs'). It distinguishes itself from the sibling get_credits by explicitly saying it answers 'where credits went'.

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?

Explicitly tells when to use ('Use this to answer where credits went') and names an alternative ('for the current balance use get_credits'). This provides direct context versus siblings.

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