Possesses an intrinsic protein tyrosine phosphatase (PTPase) activity (PubMed:9585503). Regulates egl-15 activity which is required for hypodermis-mediated fluid homeostasis and protein degradation in muscle (PubMed:9585503). During the formation of neuromuscular junctions at the larval stage, negatively regulates membrane protrusion from body wall muscles (PubMed:16495308). Plays a role in nicotinic acetylcholine receptor (nAChR)-mediated sensitivity to nicotine (PubMed:15990870). Regulates synaptic levels of nAchR subunit lev-1 in the nerve cord (PubMed:15990870). Promotes the outgrowth of the quaternary dendritic branches of the PVD sensory neurons (PubMed:26968353). In parallel to the sax-7/mnr-1 pathway, also controls the extension of the PVD primary branches (PubMed:26968353). Acts in the netrin/DCC pathway to mediate the formation of synapses between the AVA interneurons and the PHB sensory neurons (PubMed:29742100). Also required for the formation of synapses between the AVA interneurons and the VA10 motor neurons (PubMed:29742100). H2O + O-phospho-L-tyrosyl-[protein] = L-tyrosyl-[protein] + phosphate Expressed in muscles, hypodermis and a subset of neurons (PubMed:9585503, PubMed:26968353). Expressed in the AVA neurons, with high expression in the anterior half of the preanal ganglion where AVA neurons contact the PHB neurons (PubMed:29742100). Tyrosine-protein phosphatase 1 domain has enzymatic activity which is required for the negative regulation of egl-15 (PubMed:9585503). Tyrosine-protein phosphatase 1 domain is required for correct PVD dendrite formation (PubMed:26968353). The second tyrosine-protein phosphatase domain has no phosphatase activity and appears to be dispensable for clr-1 function (PubMed:9585503). Isoform c lacks both tyrosine-protein phosphatase domains and is likely to have no catalytic activity (PubMed:9585503). The extracellular domain is required for the formation of synapses between the AVA interneurons and the PHB sensory neurons. Mutants have a reduced size and a loss of both motility and fertility. In addition the pharynx and the intestine appear to float within the pseudocoelom resulting from the accumulation of fluid. The majority die during larval development with hypodermal ruptures. Simultaneous knockdown of clr-1 and egl-15 rescues the thin body morphology of egl-15 mutants. Belongs to the protein-tyrosine phosphatase family. Receptor class 2A subfamily.