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

Annotations already establish read-only, idempotent, non-destructive behavior, so the bar is lower. The description adds meaningful behavioral context: the 1000-gene batch limit, support for mixing Entrez and Ensembl IDs, and return-field parity with mygene.genes.info. It does not discuss missing-ID handling or error cases, but the output schema covers return structure and the annotations cover safety.

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?

The description is front-loaded with the action and input format, and the follow-up sentences add use cases and ID-mixing support. The returned-field list is useful but partially redundant with the schema's default `fields` description, so it is efficient rather than maximally lean.

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 batched, read-only gene lookup with an output schema, the description covers everything an agent needs to select and invoke it correctly: input ID types, maximum batch size, supported mixing, returned fields, and appropriate use cases. There are no critical gaps.

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%, so the baseline is 3. The description adds extra meaning beyond the schema by explicitly stating that mixing NCBI Entrez and Ensembl IDs in the same request is supported and by tying the fields parameter to the exact output of mygene.genes.info. This is modest but real added value.

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 ('Retrieve'), a clear resource ('annotation data for genes'), and the exact input mechanism ('comma-separated list of NCBI Entrez Gene IDs or Ensembl gene IDs'). It also distinguishes itself from the sibling mygene.genes.info by noting it returns the same fields in batch form, so an agent can tell them apart immediately.

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 clear usage context with concrete examples ('enriching gene lists from RNA-seq experiments, GWAS results, or drug target panels') and implies the batch-vs-single distinction through 'up to 1000 genes in a single request.' It does not explicitly say 'for a single gene use mygene.genes.info' or 'use search when you don't have IDs', so it stops short of full exclusion guidance.

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