There has been one announcement after another about OpenAlex, a huge bibliographic database of 248 million scientific works whose metadata is distributed under a CC0 licence, accessible via the online interface and an API. At the end of 2023, Sorbonne Université decided not to renew its subscription to the Web of Science, stating that it was not just a question of saving money but of "resolutely freeing itself from proprietary bibliometric products" and using OpenAlex. In January 2024, the CNRS announced that it would be unsubscribing from Scopus (while maintaining its subscription to WoS) and would be "gradually switching to free bibliographic tools that are compatible with the organisation's open science policy", again mentioning OpenAlex as one of the possible alternatives. Finally, in February 2024, the MESR announced a multi-year partnership with OpenAlex, with financial support and no doubt human resources to contribute "to the improvement of OpenAlex's general data and by helping to enrich in particular the data linked to French research". In view of this enthusiasm, and before signing up for the sole reason of opening up science, we felt it necessary to assess the relevance of using OpenAlex exclusively to carry out a count of publications at the level of an institution, a classic procedure when you then want to carry out a more detailed bibliometric analysis on the basis of advanced indicators. This post presents the 2 tests we carried out to answer 2 questions. Question 1: What proportion of publications already listed (in WoS, Scopus or HAL) by Ecole des Ponts can be found in OpenAlex? Question 2: What proportion of publications is correctly retrieved by OpenAlex for a query on Ecole des Ponts?