In the FPI framework, input indicators are those attributes expected to influence the outcomes of fishery management. One subset of those indicators is comanagement, measured by 11 input scores spread over four dimensions (collective action, participation, community, and gender). After applying FPIs to 13 Japanese coastal fisheries that varied in fishing method, targeted species-type, fishermen’s group characteristics, and performance outcomes, we found that comanagement scores did not vary significantly across these cases. This implies that comanagement does not affect the outcomes in these fisheries, but other studies and field observations suggest otherwise. Based on FPI case studies from Japan and elsewhere combined with on-the-ground knowledge of these fisheries and the theories of Olson, Ostrom, and Buchanan on collective action, we explore the development of an FPI add-on module to assess comanagement attributes. How to score and interpret dimensions such as the quality of co-managing organization, commitment to self-governance, rules that alter race-to-fish incentive, and consensus and common knowledge among the group members will be discussed.