An LLM such as OpenAI or Llama3.2 is basically a very large language model that is capable of auto-completing text based on the infinite number of data points that it has seen in training.
In 2023 as LLMs were being tasked to reason about things like Math, OpenAI invented a concept called Function Calling — basically the LLM would instead of only completing text answers would call an outside function (for example calculation) as part of its text generation tasks.
This opened up infinite new possibilities for LLMs to extend deeper into reasoning and interacting with the world.
CrewAI (and langchain) wraps up this concept with the abstraction of Tools, tools basically are things available for agents to use as part of completing tasks.
CrewAI-tools repo includes pre-built tools, which can be given to an agent to use as part of a crew’s tasks.
A developer can also build custom tools for application specific needs.
Some useful content below: