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

Annotations already declare readOnly, openWorld, idempotent, and non-destructive behavior, and the description adds value by specifying what results are returned: ADI, CAS number, functional class, and chemical id, plus the scope of the search across identifier types. It does not cover miss/error behavior, but with annotations this is a minor gap.

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?

Three sentences, each earning its place: what it searches, what it returns, and when to use it. The key information is front-loaded and no words are wasted.

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 single-parameter read-only lookup with no output schema, the description is nearly complete: it names inputs, examples, returned fields, and intended use. It could add behavior on ambiguous or unmatched queries, but that is a modest omission given the simple interface.

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% and the query parameter already documents name fragments, CAS numbers, and INS/E-numbers with examples. The tool description restates the same identifier formats and adds examples, but does not add meaning beyond the schema, so a baseline 3 is appropriate.

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 states a specific verb ('Look up') and a clear resource: the WHO/FAO JECFA database for food additives, flavourings, contaminants, or veterinary drugs, and lists accepted identifiers. It does not explicitly differentiate itself from siblings like jecfa_by_number or jecfa_by_functional_class, so it falls short of a 5, but the purpose 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?

It gives explicit use-case guidance: use this to answer whether a substance was evaluated and what ADI was judged acceptable. It does not mention alternatives or exclusions such as when to prefer jecfa_by_number or jecfa_by_functional_class, so it lacks the 'when not to use' component, but the context is clear.

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