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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false. The description adds behavioral context: it indicates that omitting the drug parameter changes the result from a single drug-gene entry to a list of all curated drugs for that gene. It also names the types of data returned. This is meaningful beyond 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?

Two sentences; the first states the core purpose and returned content, the second a concise conditional usage note. No filler; front-loaded and efficient.

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 simple read-only lookup with two parameters and no output schema, the description covers what it returns, the optionality of drug, and the behavior when drug is omitted. It lacks explicit return format or error conditions, but annotations cover safety and the scope is small.

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 coverage is 100%, so the baseline is 3. The description adds semantics for the optional drug parameter by explaining the effect of omission ('Omit drug to list every drug curated for that gene'), which is not present in the schema's description ('Optional'). The gene parameter is not elaborated 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?

The description clearly states a specific verb-resource: it returns pharmacogenomic guidance (CPIC/DPWG, recommendation, phenotypes, sources) for a gene, optionally filtered by drug. It does not explicitly contrast with sibling tools like lookup_gene or lookup_variant, but the drug-gene focus is apparent.

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 gives a conditional usage tip: 'Omit drug to list every drug curated for that gene,' which explains when to omit the drug parameter. However, it does not say when to prefer this tool over lookup_gene or lookup_variant, nor any exclusions or prerequisites. Usage is implied by the purpose.

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