A microsatellite (STR / SSR) is a tandem repeat of a short motif (typically 2–6 nt — di- to hexanucleotide) whose copy number varies between alleles. Amplifying across the repeat with flanking primers turns each allele into a PCR product of a distinct length, sized on a capillary-electrophoresis instrument against an internal size standard.
Paste sequences (each containing one repeat — mark it with [..] or let the tool auto-detect it; TotalRepeats finds them genome-wide). The tool designs a Tm-matched, dimer-checked primer pair in the unique flanks, optionally adds the universal tail and a reverse PIG-tail (both on by default), and assembles a multiplex panel with dye channels assigned so allele size-ranges never overlap within one colour.
[..] or rely on auto-detection
The tail (e.x. M13) enables cheap fluorescent labelling (one dye-labelled universal primer per colour); the reverse PIG-tail (GTTTCTT) promotes full +A adenylation for sharper peaks. Both 5′-tails are templated into the amplicon, so the M13 tail (+18 nt) and PIG-tail (+7 nt) are already included in the reported product and allele sizes. For >1 dye, give each channel its own universal tail.