Significant Hallucination Discrepancy: Agent Kit "Chat" Tab vs. API Workflow Integration

Hello community,

I am experiencing a critical consistency issue with an Agent I built using the OpenAI Agent Kit.

The Setup:

  • I have an Agent configured with a specific System Prompt and a set of Tools (RAG retrieval for a product catalog).

  • The goal is to retrieve specific Item UUIDs and Prices from the catalog.

The Issue:

  1. In the Agent Kit “Chat” Tab (UI): The agent works perfectly. It correctly calls the retrieval tool, reads the UUID/Price from the tool output, and refuses to answer if data is missing. Zero hallucinations.

  2. In my Workflow (API Integration): When I connect the same agent configuration to my workflow, it starts hallucinating. It invents UUIDs that don’t exist in the RAG source and makes up prices.

What I’ve Checked:

  • The System Prompt text is identical in both environments.

  • The RAG tool availability is the same.

My Question:

Are there hidden parameters or “silent” system instructions that the Agent Kit UI applies in the “Chat” tab that are NOT automatically applied when connecting via the API? specifically regarding:

  • Default Temperature settings?

  • How Tool Outputs are fed back into the context window?

  • Implicit “Strictness” controls?

Has anyone else seen this “Dr. Jekyll and Mr. Hyde” behavior between the UI and the API integration?

Thanks!

workflow image for reference: