Checklist of uncertainty information for observational data sets on ESGF being used by the Rapid Evaluation Framework (REF). This document describes the treatment of uncertainties within observational datasets with the intention of using this information within the REF, as agreed upon by the obs4MIPs Steering Panel and the CMIP REF Delivery Team and authorised for publication by the CMIP Panel. The contents of the first version of this checklist were reviewed by a group of metrology experts alongside modellers, representatives of CF conventions and model evaluation packages, led by NPL at a dedicated workshop on uncertainty metadata held at the University of Reading on the 19 August 2025. A number of changes were made as a result. The final draft of the version1.0 of this checklist was reviewed by Emma Wooliams (NPL, ESMO/WGORC). The authors of the checklist understand this might not be the preferred method of providing uncertainty information. However, this serves as a pragmatic and robust interim approach to allow for use within model evaluation of the CMIP7 Assessment Fast Track data. The current developers of the REF and its future custodians within the WCRP ESMO core project will continue engaging with the obs4MIPs Steering Panel and the model evaluation and observational science communities to refine inclusion of uncertainty information in climate model evaluation. The authors of this document wish to acknoweldge the input from attendees of the REF Hackathon which took place 10-13 March 2025, members of CMIP Panel, the Model Benchmarking co-leads, the CMIP REF delivery team and participants of the workshop on uncertainty metadata held at the University of Reading on the 19 August 2025