The Composite Indicator Analysis and Optimization (CIAO) tool v.2 is an expansion of the automated Matlab menu-version of the approach presented in 2017 by William Becker and co-authors in Ecological Indicators 80:12-22 for the advanced assessment of Composite Indicators (CIs). The CIAO tool allows users to: 1. Perform a detailed examination of the linear and nonlinear relationships among (i) the set of indicators and (ii) between the indicators and the Composite Indicator (CI). 2. Assess how the indicators are “balanced” within the CI, i.e. to what extent the influence of each indicator matches its assigned weight. 3. Tune the weights of the indicators so that the influence of each one matches pre-defined importance values.