NCBI Entrez E-utilities API

Access NCBI databases (Gene, SNP, ClinVar, Nucleotide, Protein, OMIM) through the Entrez Programming Utilities. Supports search, fetch, linking, and summary operations.

API Endpoints

Base: https://eutils.ncbi.nlm.nih.gov/entrez/eutils

Authentication & Rate Limits

Set the NCBI_API_KEY environment variable for higher throughput.

• With API key: 10 requests/second
• Without API key: 3 requests/second

Append &api_key=$NCBI_API_KEY to all requests when available.