RNA polyphosphatase which has RNA 5'-triphosphatase and diphosphatase activities (PubMed:33378643). Displays poor protein-tyrosine phosphatase activity (By similarity). Binds to 5'-triphosphorylated RNAs (also called ppp-RNAs) (PubMed:33378643). Dephosphorylates ppp-RNAs converting them to 5'-monophosphorylated RNAs (also called p-RNAs) (PubMed:33378643). During small-RNA-mediated gene-silencing or RNA interference (RNAi), involved in the dcr-1-mediated processing of an amplified dsRNA intermediate (PubMed:16439208). This is most likely in association with several components of the ERI/DICER complex including dcr-1, eri-1 and rrf-3 (PubMed:33378643). Plays a role in the biogenesis of 26G small interfering RNAs (26G-siRNAs), which are a class of 26 nucleotide siRNAs that possess a guanine residue at the 5'-end, by dephosphorylating 5'-triphosphorylated 26G-siRNAs prior to their maturation by the ERI/DICER complex (PubMed:33378643). Plays a role in the biogenesis of csr-1-bound 22G small interfering RNAs (22G-siRNAs), which are a class of 22 nucleotide siRNAs that possess a guanine residue at the 5'-end (PubMed:33378643). Not required for the biogenesis of microRNAs (miRNA) or for the biogenesis of a class of 21 nucleotide PIWI-interacting RNAs (piRNAs) that possess a uracil residue at the 5'-end (also called 21U-RNAs) (PubMed:33378643). Interacts with the ERI/DICER complex component dcr-1 (PubMed:16439208, PubMed:33378643). Interacts with ERI/DICER complex components rrf-3 and isoform b of eri-1 (PubMed:33378643). Interacts with drh-3 and rde-8 (PubMed:33378643). Expressed from embryogenesis to adulthood (PubMed:33378643). Expressed in the germline and somatic cells of L4 stage larvae (PubMed:33378643). In the germline of L4 stage hermaphrodites, uniformally expressed in germ cells from the proliferative mitotic zone to the meiotic mid-pachytene region (PubMed:33378643). Expression reduces in germ cells transitioning through diplotene and meiosis I and II and increases again before cells begin spermatogenesis (PubMed:33378643). During oogenesis, expressed in the distal germline and through the bend in the ovotestis (PubMed:33378643). Not expressed in maturing oocytes or the embryonic germline (PubMed:33378643). Expressed in most somatic cells throughout development, with high expression in intestinal cells (PubMed:33378643). Arrests at the L4 larval stage due to a failure to undergo the L4 to adult molt. Sterile due to the lack of functional gametes. In RNAi-mediated knockdown assays, fails to process dsRNA which results in the accumulation of high molecular weight dsRNA-derived RNA species. Belongs to the protein-tyrosine phosphatase family. Non-receptor class dual specificity subfamily. Two isoforms have been reported, however the molecular basis and sequence differences have not been determined. Both isoforms interact with components of the ERI/DICER complex and both are detected at all larval and adult stages, but only pir-1b is expressed in embryos (PubMed:33378643). Furthermore, pir-1a expression depends on drh-3 activity and pir-1b expression depends on dcr-1 activity (PubMed:33378643).