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

Annotations already declare readOnly, idempotent, and non-destructive behavior, so the bar is lower. The description adds meaningful behavioral context beyond that: it 'States the vintage of each number and warns when they are measured months apart,' and explains that it 'Returns whichever benchmarks exist' — valuable caveats for a data-comparison tool.

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 bit dense but every sentence earns its place: the opening states the core action, the second gives use cases, the third explains the vintage warning, and the final sentences cover partial data and authentication. It is front-loaded with the most important information and contains no fluff.

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?

Without an output schema, the description compensates by stating what is returned ('whichever benchmarks exist') and that vintage information is included. It covers the main caveats for a comparison tool. It does not mention error cases or units, but for a read-only lookup this is reasonably complete.

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 baseline is 3 even without additional explanation. The description mentions 'for one drug' and 'Keyless' but does not add new parameter semantics beyond the schema's own descriptions for 'drug' and 'ndc'. No extra detail about format or constraints is provided.

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 opens with a specific verb and resource: 'Put the two US drug price benchmarks side by side for one drug' and immediately defines the two benchmarks (NADAC and ASP limit). It clearly differentiates from siblings like nadac_price and asp_payment_limit by emphasizing the side-by-side comparison and the 'returns whichever benchmarks exist' behavior.

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 explicitly states when to use the tool: 'Use to see the spread between acquisition cost and reimbursement, or to check whether a drug is a retail or a clinic-administered product at all.' It does not name alternatives explicitly, but the positioning against individual benchmark tools is clear from the function and context.

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