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

Annotations already declare readOnly, idempotent, non-destructive; description adds data source, keyless access, graceful missing-data behavior, and a caveat that results are not an SDS. This complements the annotations without contradiction.

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 containing only necessary information: what it returns, how missing data is handled, and a safety caveat. No filler or redundancy.

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, the description covers input format, output content, missing-data behavior, and usage caveat. No important operational detail is missing.

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 covers the single 'query' parameter 100%, so baseline is 3. The description repeats the name-or-CID input form but adds no new parameter-level detail beyond the schema.

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?

States a specific verb (return), resource (GHS hazard classification), and source (PubChem). The description explicitly names the outputs (signal word and hazard statements), making its purpose unmistakable and distinct from a generic chemical_lookup sibling.

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?

Does not name an alternative tool, but clearly frames the use case: retrieving public GHS classification data from PubChem. It adds a boundary condition with the SDS disclaimer, telling the agent this is informational and not regulatory guidance, though it doesn't explicitly route to alternates.

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