get_model_breakdown

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

No annotations are provided, so the description bears full responsibility for disclosing behavioral traits. It does not mention that the operation is read-only, whether it returns historical or live data, or any potential limitations like cost calculation delays. The description is purely functional without behavioral context.

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, well-structured sentence that conveys essential information without any filler. Every word adds value, making it highly concise and easy to parse.

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 has only one optional parameter and no output schema, the description adequately explains what the tool returns (cost and session count per model). It is complete enough for a simple aggregation tool, though it could mention whether results are aggregated across all users or current user.

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?

Schema coverage is 100% for the single parameter 'days', which is adequately described. The description reinforces the time scope but does not add new semantic information about the parameter. The mention of model breakdown relates to output, not parameter semantics, so no extra value over schema.

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 verb 'Get' and the resource 'cost and session count broken down by Claude model (Sonnet, Haiku, Opus) for the last N days'. It specifies the exact models and the time scope, making it highly specific and distinguishable from sibling tools like get_quota_status or get_current_session.

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 like get_usage_insights or get_session_stats. It does not mention prerequisites, conditions, or exclusions, leaving the agent to infer usage context from the tool name alone.

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