The aim of this report is to define the interfaces for the tools used in the MT development and evaluation scenarios as included in the QTLaunchPad (QTLP) infrastructure. Specification of the interfaces is important for the interaction and interoperability of the tools in the developed QTLP infrastructure. In addressing this aim, the report provides: 1. Descriptions of the common aspects of the tools and their standardized data formats; 2. Descriptions of the interfaces for the tools for interoperability. where the tools are categorized into preparation, development, and evaluation categories including the human interfaces for quality assessment with multidimensional quality metrics. Interface specifications allow a modular tool infrastructure, flexibly selecting among alternative implementations, enabling realistic expectations to be made at different sections of the QTLP information flow pipeline, and supporting the QTLP infrastructure. D3.2.1 allows the emergence of the QTLP infrastructure and helps the identification and acquisition of existing tools (D4.4.1), the integration of identified language processing tools (D3.3.1), their implementation (D3.4.1), and their testing (D3.5.1). QTLP infrastructure will facilitate the organization and running of the quality translation shared task (D5.2.1). We also provide human interfaces for translation quality assessment with the multidimensional quality metrics (D1.1.1). D3.2.1 is a living document until M12, which is when the identification and acquisition of existing tools (D4.4.1) and the implementation of identified language processing tools (D3.4.1) are due.