atc_members

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

Annotations already indicate read-only, idempotent, and open-world behavior. The description adds valuable behavioral context: it explains that higher-level ATC queries return all member substances, that level 5 returns a single substance, and that each member includes a source_atc_code for disambiguation. It also notes RxNorm's US-centric nature, a crucial caveat.

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 structured in three short paragraphs, starting with the core purpose, followed by use cases, and ending with output details. Every sentence adds necessary information without redundancy. It is highly efficient and scannable.

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?

Given the tool's simplicity (one parameter, no nested objects) and the existence of an output schema, the description provides complete context: it covers when to use, what the output contains, and a data quality caveat. There are no obvious gaps for an agent to misunderstand.

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?

Although the schema already describes the atc_code parameter (100% coverage), the description adds significant semantic value by explaining how different ATC levels affect the result set and mentioning the source_atc_code in the output. This goes well beyond what the 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 starts with a clear verb+resource pair: 'List the drugs (substances) that belong to an ATC class.' This immediately distinguishes it from siblings like atc_lookup (which likely retrieves a specific code's details) and atc_classify (which classifies a drug into ATC). The explicit use cases further solidify its role.

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 explicitly lists three use cases for the tool, making its intended applications very clear. However, it does not explicitly state when NOT to use it or compare it to alternatives (e.g., atc_lookup), which would merit a 5. The listed use cases are still highly directive.

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