ensembl_region

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

Annotations already declare readOnlyHint=true and openWorldHint=true. The description adds valuable behavioral context beyond this: output is capped at the limit with a truncated marker, the current assembly is specified as GRCh38 for human, and spans should be kept modest. It does not contradict the annotations and gives the agent practical knowledge about response handling.

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 compact and front-loaded: the first sentence states purpose and payload, the second gives a concrete use case, and the third provides operational guidance and sibling routing. Every sentence earns its place with zero repetition of schema content.

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 4-parameter read-only tool with no output schema, the description covers what is returned, how output is truncated, which assembly is used, and when to choose alternatives. It does not describe the exact response format, but the field-level detail (stable IDs, rsIDs, consequence terms) plus the truncation note make the tool sufficiently complete for correct invocation.

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 structured schema already documents all parameters. The description adds contextual nuance (assembly, span caution, output cap) that enriches the region parameter semantics, but does not materially expand on limit, species, or features beyond what the schema provides. This matches the baseline-3 expectation for fully covered schemas.

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 opens with a specific verb and resource ('Query what lives in a genomic interval') and enumerates exact content: genes/transcripts with stable IDs, symbols, biotypes, and variants with rsIDs, alleles, consequence terms, and clinical significance. It also explicitly distinguishes itself from siblings like genbank_get and gene_get/variant_get, making its scope 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?

Provides a clear use case ('Ideal for locus triage — what genes and known variants sit in this GWAS hit interval?'), a recommendation ('Keep spans modest (<1 Mb recommended)'), and explicit routing to alternatives ('For sequence text use genbank_get; for entity-level annotation chain IDs into gene_get / variant_get').

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