With the All the Agents Challenge at the 20th edition of the International Semantic Web Conference (ISWC) in 2021, we organisers wanted to further advance the efforts that bring two strands of work together: 1. The original vision for the Semantic Web, formulated around 2001, in which agents played a big part, but had not fully materialised. 2. Recent progress in research, standardisation and technology around the Web of Things, the Linked Data Platform and the Social Linked Data (Solid) platform, which can enable new use-cases and provide a substrate for agent technologies on the Semantic Web. This bridging of technologies and communities has also been the topic of the Dagstuhl seminar “Autonomous Agents on the Web”1 held in Feburary 2021. Therefore, for the 20th edition of the ISWC conference and in spirit of Jim Hendler’s op-ed that asked “Where are all the agents?”, we posed the “All the Agents Challenge” (ATAC) to the Semantic Web community: To build agents that do things on Linked Data Conceptually, we assume agents that operate on a shared environment accessible via Linked Data interfaces. To allow the authors to focus on the agent part, the organisers prepared two environments, while not restricting the authors to bring their own: • The Autonomous Maze Environment Explorer Project (AMEE) by Mike Amundsen provides an environment for agents that have to escape a maze by following hypermedia affordances. AMEE can simulate mazes of different sizes. The organisers provide a RDF version of AMEE. • The Building on Linked Data (BOLD) environment is a description of a large real-world building (two floors, over 250 rooms) with simulated occupancy and sunlight. Agents can read occupancy and light level in rooms values through sensors. Agents can also actuate light switches located in the rooms. We managed to solicit six submissions in the form of paper+video+code and subjected those submissions to the following process.