I am building a ChatGPT agent in the Agent Builder interface and I have hit a road-block: I need to pass user-specific data into the conversation as a dynamic variable and then reuse it reliably in later turns. What I expect from you • A concise, step-by-step explanation (screenshots or short screencast welcome) that shows exactly where and how to declare the variable, ingest the value at run-time, and reference it in subsequent prompts or function calls. • Any required JSON schema, prompt-template syntax, or function-calling example that demonstrates the approach. • A minimal working example I can paste into a fresh agent to verify that the variable persists correctly for a single user while remaining isolated from other sessions. Acceptance criteria 1. I copy your example into Agent Builder 2. I can set a sample value (e.g., api_key, base_url) at run-time. If you have alternative techniques—such as leveraging the Assistant API or an external store—feel free to outline them briefly, but the main deliverable must work natively inside Agent Builder.