diff --git a/aws-transform-agent-toolkit/steering/agent-registration.md b/aws-transform-agent-toolkit/steering/agent-registration.md
index 8f93a08..383e6ee 100644
--- a/aws-transform-agent-toolkit/steering/agent-registration.md
+++ b/aws-transform-agent-toolkit/steering/agent-registration.md
@@ -53,6 +53,29 @@ client = boto3.client(
 
 **NEVER omit the endpoint URL** — without it, the CLI/SDK will attempt to resolve a non-existent endpoint and fail.
 
+## Agentic API Endpoint (Runtime)
+
+The Agentic API (`transformagenticservice`) is used at runtime for operations like InvokeAgent, SendMessage, ListAgentInstances, and subagent discovery. Like the Registry API, it requires an explicit endpoint.
+
+**In managed compute** (Bedrock AgentCore, MDE): The `QT_AGENTIC_API_ENDPOINT` environment variable is automatically injected by the platform.
+
+**For local development**: Set it explicitly:
+
+```bash
+export QT_AGENTIC_API_ENDPOINT=https://iad.prod.agenticapi.elastic-gumby.ai.aws.dev
+```
+
+| Stage | Region | Endpoint URL |
+|-------|--------|-------------|
+| prod | us-east-1 | `https://iad.prod.agenticapi.elastic-gumby.ai.aws.dev` |
+| prod | eu-central-1 | `https://fra.prod.agenticapi.elastic-gumby.ai.aws.dev` |
+| gamma | us-east-1 | `https://iad.gamma.agenticapi.elastic-gumby.ai.aws.dev` |
+| gamma | us-west-2 | `https://pdx.gamma.agenticapi.elastic-gumby.ai.aws.dev` |
+
+The SDK's `get_agentic_api_client()` factory reads this variable. Without it, boto3 attempts to resolve a non-existent public endpoint and fails.
+
+**NEVER use raw `boto3.client('transformagenticservice')` without setting `endpoint_url`** — use `get_agentic_api_client()` from the SDK which handles this automatically.
+
 ## Registration Flow
 
 1. **Build & containerize** your agent
diff --git a/aws-transform-agent-toolkit/steering/getting-started.md b/aws-transform-agent-toolkit/steering/getting-started.md
index b33a3bf..75a909b 100644
--- a/aws-transform-agent-toolkit/steering/getting-started.md
+++ b/aws-transform-agent-toolkit/steering/getting-started.md
@@ -18,6 +18,21 @@ Before starting, ensure you've completed the onboarding steps:
 
 **If you haven't done this yet**: The AWS Transform Agent Toolkit onboarding walks you through all installation steps. Kiro will guide you through tool validation, SDK installation, and hook setup when you first activate the power.
 
+## Environment Variables
+
+These environment variables configure the SDK at runtime:
+
+| Variable | Required | Description |
+|----------|----------|-------------|
+| `QT_AGENTIC_API_ENDPOINT` | Yes (local dev) | Agentic API endpoint URL. Auto-injected in managed compute. See [agent-registration.md](./agent-registration.md) for endpoints per stage. |
+| `WORKSPACE_ID` | Yes | ATX workspace identifier |
+| `JOB_ID` | Yes | Current job identifier |
+| `AGENT_INSTANCE_ID` | Yes | Agent instance identifier |
+| `AWS_REGION` | Yes | AWS region for Bedrock model inference |
+| `ATX_USE_MOCK_REGISTRY` | No | Set to `true` for offline development without platform connectivity |
+
+For full endpoint details, see the [Agent Registration Guide](./agent-registration.md#agentic-api-endpoint-runtime).
+
 ## What You Can Build
 
 With AWS Transform, you create two types of agents: