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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false. The description adds value beyond these by stating that the tool supports either an RxCUI or an NDC as input, implying a mutually exclusive lookup behavior. This is useful operational detail not present in the 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 core purpose, and uses bullets to enumerate the tool's functions. The final sentence provides the essential input convention. There is no wasted prose.

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?

For a simple two-parameter lookup tool with full schema coverage, relevant annotations, and an output schema present, the description provides all necessary guidance: what the tool maps, the supported directions, and the expected input. Nothing critical is missing.

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 both parameters are already described in the input schema. The description reinforces the 'either/or' semantics but does not add substantial new meaning beyond the schema entries, so the baseline score of 3 applies.

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 bidirectional mapping action between RxNorm concepts and NDC codes, then enumerates the two main use cases: getting NDCs for an RxCUI and finding an RxCUI for an NDC. This clearly differentiates the tool from sibling RxNorm tools such as rxnorm_search or rxnorm_concept, which handle different lookup concerns.

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 'Use this tool to' section explicitly lists the scenarios where the tool applies, and the final sentence tells the caller which input to provide. It does not mention alternatives or exclusion conditions, but the context is clear enough for an agent to select this tool for NDC/RxCUI cross-referencing.

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