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

Annotations already declare read-only, idempotent, open-world, non-destructive behavior, so the safety profile is covered. The description adds a genuinely useful trait not present in structured data: the pricing model (free within a daily allowance, then $0.001 USDC per call via x402), which is important for an agent to know before invoking.

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 tight sentences that are front-loaded with the returned fields and follow with the cost model. Nothing is wasted, though it is terse enough to leave usage context unaddressed.

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?

An output schema exists, so return values need not be described, and annotations cover the safety profile. For a single-parameter lookup, the description covers the essential behavior (what is returned plus cost), though the absence of any routing guidance keeps it from being fully 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?

With a single parameter and 100% schema description coverage, the schema fully documents rxcui, so the baseline is 3. The description does not add any format or syntax detail about the RxCUI beyond what the schema states.

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 names the specific fields returned (name, synonym, term type, active/obsolete status) and the resource (an RxCUI), which clearly distinguishes it from siblings like rxnorm__related or rxnorm__approximate. It stops short of explicitly naming an alternative, but the scope is unambiguous.

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?

No when-to-use or when-not-to-use guidance is given. With siblings such as rxnorm__rxcui, rxnorm__related, and rxnorm__drugs available, the description never explains which lookup to pick for which need, leaving the agent to infer from the name alone.

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