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

With readOnlyHint=true, the description adds rich behavioral context: it explains the step-function nature (only change points returned), handles multiple changes per day, and clarifies series labeling with qualifiers for collisions. This goes well beyond what annotations provide.

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 front-loaded with the core purpose and is mostly efficient, though the series labeling example adds some specificity that could be considered slightly verbose. Every sentence contributes to understanding the output.

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 no output schema and a read-only tool, the description is nearly complete—it covers return format, edge cases, and series labeling. However, it doesn't explicitly state if dates are inclusive (though the schema does) or how to interpret the price dimension labels beyond the collision example.

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%, so the baseline is 3. The description adds meaning by explaining return format ('Each point is [date, amount]') and duplicate-date handling, but doesn't elaborate on the 'from'/'to' parameters beyond the schema's 'ISO date, inclusive'.

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 states a specific verb ('Returns') and resource ('a model's price over time'), making the purpose immediately clear and distinguishable from siblings like get_model_price.

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?

It implies usage for tracking price changes but doesn't explicitly say when to use this tool versus alternatives like get_model_price or compare_models. No when-not or alternative guidance is provided.

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