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

readOnlyHint=true already tells the agent this is a safe, non-mutating read, so the description only needs to add context. It contributes the REST endpoint, but says nothing about behavior when a concept has no NDCs, whether multiple NDCs return as a list, or whether the result is paginated.

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?

Two short sentences, front-loaded with what is returned; the endpoint line is useful but slightly redundant given the preceding description. No filler or repetition.

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 single-parameter read lookup with readOnlyHint declared and no output schema, the description covers what the tool returns and how it maps to the API. It is nearly complete, though a note on empty results would close the last gap.

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% with a single required rxcui parameter that is documented in the schema, so baseline 3 applies. The description's endpoint template reinforces that rxcui is the sole input, but adds no format or validity detail beyond the schema.

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?

States a specific verb (get) and resource (NDCs for a concept), plus the expansion of the acronym and the underlying endpoint. It does not explicitly contrast itself with related siblings such as rxnorm_get_all_related, but the resource is distinctive enough that an agent can pick it out.

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?

There is no when-to-use guidance, no statement of preconditions (e.g. that a valid RxCUI is needed first, obtainable via rxnorm_find_rxcui_by_name), and no mention of alternatives among the many sibling lookups. The agent must infer usage entirely from the name.

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