apibase

Look Up Gene by Official Symbol

mygene.genes.symbol

Read-onlyIdempotent

Find a gene by its official gene symbol with an exact match for a specific species. Returns a single best-matching gene with full annotation: NCBI Entrez Gene ID, Ensembl gene ID, gene name, type, taxon, summary, UniProt accession, genomic coordinates, pathway memberships, and GO terms. Faster and more precise than full-text search when the official symbol is known. Case-insensitive (BRCA1, brca1, Brca1 all match). For human genes, use HGNC symbols (e.g. "TP53", "EGFR", "KRAS", "VEGFA"). Results can be used directly with mygene.genes.batch for comparative multi-gene analysis.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`fields`	No	Comma-separated fields to include in the response. Default includes: symbol, name, taxid, entrezgene, type_of_gene, summary, ensembl, uniprot, alias, genomic_pos, pathway. Use "all" for complete gene annotations.
`symbol`	Yes	Official HGNC gene symbol (for human) or equivalent gene symbol in the target species. Case-insensitive (e.g. "BRCA1", "TP53", "EGFR", "KRAS"). Performs an exact symbol match and returns the single best-matching gene.
`species`	No	Target species for the symbol lookup. Common values: "human", "mouse", "rat", "fruitfly", "zebrafish", "chicken", "pig", "dog". Can also use NCBI taxid (e.g. "9606" for human). Defaults to "human".	human

Output Schema

TableJSON Schema

Name	Required	Description	Default
`error`	No	Present only when the call failed. Includes error code, message, request_id, and any provider-specific extras.
`result`	No	Tool response payload. Shape varies per tool — consult the tool description and inputSchema. May be an object, array, string, or number depending on the upstream provider response.

Schema Changelog

Changes observed during successful MCP inspections.

First observedSep 22, 2026

TDQS

A4.6/5.0

Behavior4/5

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

Annotations already cover the read-only, idempotent, non-destructive safety profile, so the description does not need to re-explain those. It adds valuable behavioral detail beyond annotations: exact match, case-insensitive matching, single best-matching result, and the full annotation payload.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is longer than average but every sentence contributes: exact-match behavior, return payload, comparison to full-text search, case-insensitivity, human-specific guidance, and downstream integration. The return-field list is dense, but it is informative rather than filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the output schema, annotations, and rich parameter schema, the description covers everything needed to select and invoke the tool correctly. It explains match semantics, species context, naming conventions, when to use alternatives, and how results can feed into batch analysis. No material gap remains.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the parameters are already well documented. The description adds useful context by explaining that the symbol must be the official symbol, stating the HGNC convention for human genes, and showing example symbols. Some details duplicate the schema, but the naming-standard guidance adds real value.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description opens with a specific action: 'Find a gene by its official gene symbol' and immediately qualifies it with 'exact match for a specific species.' It clearly distinguishes itself from full-text search siblings by emphasizing official-symbol lookup and single best-matching gene retrieval.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description explicitly states when this tool is preferred: 'Faster and more precise than full-text search when the official symbol is known.' It also provides human-specific guidance (use HGNC symbols), gives concrete examples, and directs agents to mygene.genes.batch for comparative multi-gene analysis.

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

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