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

With no annotations, the description must carry the full burden. It indicates a read-only 'analyze' operation and the grouping by model, but it omits details such as whether special permissions are required, whether data is real-time or aggregated, or how edge cases (e.g., no data) are handled.

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, front-loaded sentence with no redundancy. It efficiently communicates the purpose without extra words.

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?

There is no output schema, so the description should explain return values. It mentions 'broken down by model' which implies the response will include model names and costs, but it does not specify fields like currency, cost amounts, or whether it returns a time series. Adequate for a simple tool but incomplete for precise usage.

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 input schema provides descriptions for both parameters with 100% coverage. The description reinforces the team and time-window aspects but adds no additional meaning beyond what the schema already specifies.

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 is specific and clear: 'Analyze costs broken down by model' identifies the verb (analyze), resource (costs), and grouping dimension (model). It distinguishes itself from sibling tools like budget_alert or cost_forecast by focusing on per-model cost breakdown.

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 implies the tool is for per-model cost analysis over a time window, but it does not explicitly state when to use this tool versus alternatives like cost_forecast (future predictions) or cost_tracker (general tracking). No exclusions or alternative tool references are provided.

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