feat: tool usage

[pkarw]

LLM's are great with following examples. Let's add an usage required attribute when defining the tools - for providing example values of the tool parameters and let's add it to agent context with the list of available tools @grabbou wdyt?

[grabbou]

We should think about it more carefully, as OpenAI has limits around total length of functions, so the more we add to "usage" or "response", the less functions agents can have.