Toolformer is a training-time approach that enables tool-use in LLMs by embedding tool-use decisions directly into its weights during training. It extends a language model's capabilities by augmenting model behavior through self-supervised learning, allowing the model to autonomously decide when and how to call external APIs during inference. In contrast, Model Context Protocol (MCP) is a runtime-first approach that provides a standardized protocol for tool access, allowing any compatible LLM to interact dynamically with external systems through structured, interpretable calls. While Toolformer offers a lightweight and self-contained way to simulate tool-use in language models, its design imposes several limitations, including requiring fine-tuning on tool-augmented data, tools must be defined before training, no runtime tool execution, inflexible to tool changes, inaccessible to API-based or black-box models. MCP, on the other hand, is designed for scenarios where language models must interact with external tools, systems, or memory during inference, without retraining or tightly coupling tool logic to the model itself. Its architecture introduces several practical constraints, including requiring structured output from the model, relying on external infrastructure, not suitable for offline or disconnected environments, requiring server-side tool hosting and maintenance, and security and error handling must be managed externally. Ultimately, the choice between Toolformer and MCP depends on the specific use case and requirements of the system being built.