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

Beyond the readOnlyHint annotation, the description adds valuable context: spending is gross before manufacturer rebates, defaults to the newest year, and returns specific fields like brand name, generic name, and total spending. This enriches the agent's understanding without contradicting annotations.

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 concise, front-loaded with the main action, and every sentence adds value—purpose, example queries, return fields, and a key nuance about gross spending. No filler 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?

The tool is simple (two optional params, no nested objects) and has an output schema. The description nevertheless explains return fields, default behavior, and the gross-spending nuance, making it complete for the agent to invoke correctly without additional info.

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 description coverage is 100%, so the schema already fully documents both parameters. The description repeats the default-year behavior already in the schema but adds no additional parameter-specific meaning. It efficiently hits the baseline for high schema coverage.

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 uses a specific verb ('Rank') with a clear resource ('Medicare Part D drugs') and scope ('by total gross spending for a year'). It also provides example questions ('which drugs have the highest Medicare Part D spending') that precisely define the tool's purpose and differentiate it from general drug spending tools.

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 clearly implies when to use the tool: for ranking top Part D drugs by cost. It does not explicitly exclude alternatives or mention sibling tools, but the context is clear enough for an agent to select it for the intended use case.

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