The issue of miracle's indication on the truthfulness of the prophet's claim is one of the fundamental topics in Islamic theology. This research critically examines the mechanism of miracle's indication in proving prophethood from the perspective of Ash'ari and Mu'tazili schools, with emphasis on Imamiyyah teachings. The main question is how the mechanism of miracle's indication on the truthfulness of the prophet's claim is explained according to Ash'ari and Mu'tazili, and what criticisms are directed at them based on the Imamiyyah view. The hypothesis is that the Imamiyyah approach, relying on rationality and philosophical principles, presents a solid and defensible indication for miracle that is not found in other schools. The research method is analytical-critical, based on theological and philosophical sources of the three schools. Findings show that Ash'ari consider miracle's indication as sam'i (auditory/revelation-based), meaning it is only comprehensible through religious transmission; while Mu'tazili consider it as wad'i (conventional), meaning based on divine convention. Both approaches face indicational and epistemological challenges. However, Imamiyyah, by relying on its epistemological and anthropological foundations and proper application of rules such as the principle of grace (lutf), rational goodness and badness (husn wa qubh), and the ugliness of leading to ignorance (qobh eghra' be jahl), establishes a logical and rational connection between miracle and the truthfulness of the claimant that addresses these challenges. Therefore, the Imamiyyah theory in proving prophethood possesses greater epistemological coherence and is more effective in rational dialogue.