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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds value the annotations cannot: it discloses the shape of what comes back (variant rsIDs, phenotypes, array coverage limits) and hints at caveats with 'what a consumer genotyping array can and cannot tell you'. It does not cover behavior on an unknown or ambiguous symbol, which keeps it below a 5.

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?

A single front-loaded sentence with no preamble or filler; every item in the enumeration describes a distinct category of returned data. It is a dense list rather than prose, but nothing is redundant.

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 no output schema, the description carries the burden of describing return values, and it does so explicitly by listing the content categories. For a one-parameter read tool with full annotation coverage, little else is essential; only error/ambiguity behavior is unaddressed.

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 states 'HGNC gene symbol, e.g. CYP2C19. Case-insensitive.' The description adds nothing about the symbol parameter — no mention of accepted aliases, what happens on an invalid symbol, or lookup precision. Baseline 3 is correct where the schema does all the work.

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 (one gene) and enumerates the curated content returned: function, variants with rsIDs, phenotypes, drug interactions, array coverage, sources. That is concrete enough for an agent to know what it retrieves. It does not, however, distinguish itself from siblings like lookup_variant or lookup_drug_gene, which plausibly return overlapping data.

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?

Usage is only implied by the content list — an agent infers it should call this when it has a gene symbol and wants a broad summary. There is no explicit when-to-use, no exclusion, and no pointer to lookup_drug_gene or lookup_variant for narrower questions. The single required symbol parameter hints at the entry condition but that is left to the schema.

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