Agree with @lrhyne 's hypothesis here that it is worth checking the size of the content you are passing in on each of your document objects.
In terms of configuration options, assuming you are passing these using the Ontology Context for your Agent, you should be able to configure the properties of the object type which are passed to the Agent (see attached example from the Ontology Context documentation).
You can also configure the number of relevant objects which are returned to the Agent from the retrieval (the default is 5).
If the document content is too large for the model’s context window to pass as a single object, you will need to update your document pipeline to implement chunking and embedding of the document content and use this chunk object type in your Ontology context to only retrieve relevant chunks of content to the current user query (see related answer here)