Langflow

Langflow lets builders arrange models, prompts, data sources, and tools as a visual flow while retaining Python-based extensibility. The official documentation covers agents, API-triggered flows, custom components, and Model Context Protocol connections. It is open source, but any hosted model calls, infrastructure, or commercial service have their own costs. A flow is most valuable when it can be reproduced and tested: save versions, keep secrets outside the graph, and run inputs that challenge retrieval and tool-use assumptions. If a component performs an external action, define what happens when the model selects the wrong tool.