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

Annotations already cover readOnly, idempotent, openWorld and non-destructive behavior, so the safety profile is free. The description adds genuinely new operational context: a metered pricing model (free within a daily allowance, then $0.002 USDC per call via x402) that an agent cannot learn from structured fields.

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 tightly written sentences, front-loaded with what is returned and how it is grouped, followed by the cost condition. No filler or redundancy.

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?

With an output schema present, return values need no explanation, and the annotations plus pricing disclosure cover most of what an agent needs for a one-parameter lookup. The only real gap is routing relative to the other rxnorm tools, which is not addressed.

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?

There is a single parameter with 100% schema description coverage ('Drug name (ingredient or brand)'), so the schema does the work. The description's 'for an ingredient or brand name' merely restates it without adding format, casing or normalization guidance.

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 resource and scope: returns clinical drugs, branded drugs and packs for an ingredient or brand name, grouped by RxNorm term type. That is more specific than a bare 'get drugs', but it never distinguishes itself from siblings like rxnorm__approximate, rxnorm__spelling or rxnorm__rxcui, which an agent must choose between for name-based lookups.

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 phrase 'for an ingredient or brand name' implies the input context and therefore when the tool applies, but there is no explicit when-to-use or when-not-to-use guidance and no mention of the sibling tools that handle fuzzy spelling, codes or related concepts. Usage is left to inference.

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