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

Annotations already declare readOnly, idempotent and openWorld, so the safety profile is covered; the description adds real value beyond that by disclosing paging behaviour (live genes/phenotypes) versus complete-vocabulary static topics, and by describing that phenotypes preserves distinct activity-score rows, frequencies and consultation text. Return shape detail is somewhat redundant with the existing output schema.

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 dense sentences, each carrying distinct information (coverage, phenotypes nuance, paging/static split, downstream use). The opening sentence is a long enumeration but is front-loaded with the tool's scope, and nothing is padding.

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?

With annotations, a full output schema and 100% schema coverage, the description supplies the remaining context an agent needs: static vs live behaviour, the geneSymbol dependency for phenotypes, and the intended downstream chaining. Complete enough to call correctly without opening the schema.

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 schema already documents limit clamping, zero-based offset with nextOffset, and geneSymbol's per-topic requirement. The description only reinforces the phenotypes/geneSymbol dependency and mentions paging generically, adding little syntax or semantics beyond the schema. Baseline 3 applies.

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 the resource concretely, enumerating the six reference vocabularies (gene symbols, CPIC levels, ClinPGx testing labels, classifications, input formats, phenotypes) that the tool exposes. It also distinguishes itself from siblings by framing the output as input to later 'discovery, diplotype and recommendation calls'. It stops short of naming a specific sibling it replaces, but the verb+resource 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 clear usage context: use the results to feed subsequent discovery, diplotype and recommendation calls, and notes that static topics need no upstream request while genes/phenotypes are live. The phenotype prerequisite (geneSymbol) is stated. What's missing is an explicit statement of when to pick this over a specific sibling such as pgx_search_alleles.

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