BACKGROUND: Identifying what a communication partner is looking at (referential intention) and why (social intention) is essential to successful social communication, and may be challenging for children with social communication deficits. This study explores a clinical task that assesses these intention-reading abilities within an authentic context. AIMS: To gather evidence of the task's reliability and validity, and to discuss its clinical utility. METHODS & PROCEDURES: The intention-reading task was administered to twenty 4-7-year-olds with typical development (TD) and ten with autism spectrum disorder (ASD). Task items were embedded in an authentic activity, and they targeted the child's ability to identify the examiner's referential and social intentions, which were communicated through joint attention behaviours. Reliability and construct validity evidence were addressed using established psychometric methods. OUTCOMES & RESULTS: Reliability and validity evidence supported the use of task scores for identifying children whose intention-reading warranted concern. Evidence supported the reliability of task administration and coding, and item-level codes were highly consistent with overall task performance. Supporting task validity, group differences aligned with predictions, with children with ASD exhibiting poorer and more variable task scores than children with TD. Also, as predicted, task scores correlated significantly with verbal mental age and ratings of parental concerns regarding social communication abilities. CONCLUSIONS & IMPLICATIONS: The evidence provides preliminary support for the reliability and validity of the clinical task's scores in assessing young children's real-time intention-reading abilities, which are essential for successful interactions in school and beyond.