To support informed and responsible use of CDS datasets, C3S has established an EQC framework that combines quality assurance, scientific quality assessment, and fitness-for-purpose guidance. The EQC framework is designed as an operational component of the CDS, ensuring that quality-related information is maintained over time, aligned with the evolving CDS catalogue, and made accessible to users in a consistent and transparent manner. EQC activities shall support both direct user access to quality information and integration with an emerging LLM-based search and discovery service. The successful Tenderer shall contribute to the delivery and operation of EQC activities as an integrated CDS service, supporting consistency, transparency, and sustainability across datasets and services. In particular, the successful Tenderer shall: support the planning, coordination, and operational delivery of EQC activities across all CDS dataset categories; contribute to the production, maintenance, and review of authoritative quality and fitness-for-purpose information; ensure that EQC outputs are aligned with CDS governance, dataset roadmaps, best practices, validation protocols, technical standards and scientific review processes; support the effective communication of quality-related information to users and user-facing services; produce ad-hoc quality assessment on specific topics as requested by ECMWF.