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

Annotations already establish read-only, idempotent, non-destructive behavior. The description adds useful behavioral context beyond that: results are limited to active ingredients, it can reveal single vs. multi-ingredient status, and it returns ingredient RxCUIs and names.

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 short, front-loaded with the core action, and uses a tight bullet list plus a return-summary line. Each sentence adds functional or scoping value rather than repeating schema content.

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 one-parameter tool with a full schema and output schema, the description covers input, scope, use cases, and return contents. It does not address invalid/missing RxCUI behavior, but that is a minor gap given the output schema and simple validated input.

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?

The schema already covers the only parameter fully with a description, pattern, and required status. The description only restates 'by RxCUI' and does not add extra parameter semantics, so this is at the baseline.

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: 'Get active ingredients for a drug by RxCUI.' The follow-up bullets clarify intended use cases, and the tool is easily distinguished from sibling RxNorm tools like rxnorm_search or rxnorm_concept because it is explicitly scoped to ingredient lookup.

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 gives explicit contexts: find active ingredients, check single vs. multiple ingredients, identify generic components. It does not name alternatives or say when not to use it, so it falls one step short of full routing guidance.

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