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

The annotations already declare readOnly, idempotent, openWorld, and non-destructive behavior, so the description's main job is to add context beyond that. It does so by specifying the return content (titles, URLs, plain-language summaries), noting English/Spanish response support, and stating there is no auth and unlimited free usage. This is useful behavioral and operational context that annotations do not convey.

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 compact and front-loaded with the core purpose, followed by useful examples, optional-parameter guidance, language support, and source/licensing details. Every sentence serves a purpose, and there is 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?

The tool is low in complexity, has 100% schema parameter documentation, rich annotations, and an output schema. The description adds the remaining operational context an agent needs: the service source, no-auth access, unlimited free usage, language options, and how to improve matching. Nothing essential is missing for correct selection and invocation.

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%, with each parameter already explained in the schema, so the baseline is 3. The description reinforces the examples and explains that display_name improves match accuracy, but this largely overlaps with what the schema already states. It does not add materially new parameter semantics beyond what the structured schema provides.

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-resource pair: 'Look up patient-friendly drug information for an RxNorm concept ID (RXCUI) via the NLM MedlinePlus Connect service.' It names the exact return artifacts (titles, URLs, plain-language summaries) and gives concrete RXCUI examples, making the tool's function unambiguous. The focus on RxNorm distinguishes it from the sibling medlineplus ICD/SNOMED lookup tools.

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 description clearly indicates when this tool is appropriate: when an agent has an RxNorm concept ID and wants patient-friendly MedlinePlus drug content. It also provides practical guidance such as supplying optional display_name to improve match accuracy and using language=es for Spanish responses. However, it does not explicitly mention sibling alternatives or cases where another lookup tool would be preferable, so it stops short of full exclusions.

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