usage_by_model

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It states the tool breaks down usage and cost but doesn't describe what 'break down' entails (e.g., aggregated metrics, detailed logs, cost calculations), whether it requires specific permissions, rate limits, or what the output format looks like. For a tool with no annotations and no output schema, this leaves significant behavioral gaps.

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, efficient sentence that front-loads the core purpose without unnecessary words. It directly communicates what the tool does without redundancy or fluff, making it easy to parse quickly.

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 complexity (analyzing usage and cost data), lack of annotations, and no output schema, the description is incomplete. It doesn't explain what 'break down' means in terms of output structure, data granularity, or behavioral traits like error handling. For a tool with four parameters and no structured output information, more context is needed to guide effective use.

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 has 100% description coverage, clearly documenting all four parameters. The description adds minimal value beyond the schema, only implying that parameters define a 'time period' and optional filtering. It doesn't provide additional context like how 'environment' relates to models or what 'limit' affects in practice. With high schema coverage, the baseline score of 3 is appropriate.

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 the tool's purpose: 'Break down usage and cost by AI model over a time period.' It specifies the verb ('break down'), resource ('usage and cost'), and scope ('by AI model over a time period'). However, it doesn't explicitly differentiate from its sibling 'usage_by_service', which appears to be a similar breakdown tool but by service instead of model.

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 no guidance on when to use this tool versus alternatives. It doesn't mention sibling tools like 'usage_by_service' or 'get_cost_analysis', nor does it specify prerequisites, exclusions, or optimal use cases. The only implied context is needing usage and cost data by model over time.

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