MASRML–Multi-Agent Systems Requirements Modeling Language–is a UML-based Domain-Specific Modeling Language conceived for the requirements modeling in multi-agent system projects. Along this work the extended metamodel developed to support the language is described and the applicability of this DSML in the requirements identification of a multi-agent system is demonstrated using the new mechanisms produced to model specific functional requirements for this kind of system. This work also includes how the DSML was validated and the impressions collected during the validations.