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

Annotations already establish read-only, idempotent, and non-destructive behavior. The description adds useful behavioral scope by indicating the tool returns a category-wide list and that each entry includes ADI and CAS numbers, while not contradicting the annotations.

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 two sentences, front-loaded with the operation and scope, and every sentence carries useful information. There is no filler or repetition of obvious details.

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 one-parameter read-only listing tool, the description gives scope, output fields, and usage guidance. It does not discuss pagination, case sensitivity, or exact matching behavior, but the simple signature and strong annotations make these non-critical for correct 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?

The schema already documents the single parameter fully, so this is a baseline-3 case. The description adds value by enumerating example functional classes and the four exact group names, which helps the agent construct valid input values despite no enum list.

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 a specific verb ('List every substance') and resource (substances in a functional class or one of four groups), with concrete examples. It also contrasts the tool with single-substance lookup, helping differentiate it from sibling tools like jecfa_chemical and jecfa_search.

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?

It provides an explicit decision rule: 'Use to survey what is permitted in a category rather than to look up a single substance.' This gives clear when-to-use and when-not-to-use guidance, though it does not explicitly name the alternative sibling tools.

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