# Runtime Evaluation

Evaluations play a crucial role in improving LLM app outputs by altering execution flow at runtime.

TruLens supports runtime evaluation via two different mechanisms:

1. [In-line Evaluations](/content/component_guides/runtime_evaluation/inline_evals/index.html) - evaluations that are executed during an agent's execution flow and passed back to agent to assist in orchestration.
2. [Guardrails](/content/component_guides/runtime_evaluation/guardrails/index.html) - evaluations that can be used to block input, output and intermediate results produced by an application such as a RAG or agent.