This PR adds a comprehensive model card to the repository, which previously had placeholder content.
The model card now includes:
* Links to the associated paper ([Chain-of-Agents: End-to-End Agent Foundation Models via Multi-Agent Distillation and Agentic RL](https://huggingface.co/papers/2508.13167)), the project page, and the GitHub repository.
* Essential metadata: `license: apache-2.0`, `library_name: transformers`, and `pipeline_tag: text-generation`, enhancing discoverability on the Hugging Face Hub.
* A detailed overview of the Chain-of-Agents (CoA) paradigm and Agent Foundation Models (AFM), incorporating key features and performance highlights.
* A Python code snippet demonstrating how to use the model for inference with the `transformers` library, including usage of the Qwen2 chat template.
* The appropriate BibTeX citation for the work.
Please review and merge this PR.
