Update ADK doc according to issue #1650 - 1

docs/integrations/agent-identity.md

@@ -0,0 +1,34 @@
+---
+catalog_title: Agent Identity
+catalog_description: Manages the complete lifecycle of an access token using the GCP Agent Identity Credentials service.
+---
+
+# Agent Identity
+
+## Installation
+
+```bash
+pip install "google-adk[agent-identity]"
+```
+
+## Global Registration
+
+Register the provider globally in your application:
+
+```python
+from google.adk.auth.credential_manager import CredentialManager
+from google.adk.integrations.agent_identity import GcpAuthProvider
+
+CredentialManager.register_auth_provider(GcpAuthProvider())
+```
+
+## Toolset Configuration
+
+To use the Agent Identity provider with a specific toolset, define the scheme and pass it to the toolset's constructor.
+
+```python
+from google.adk.integrations.agent_identity import GcpAuthProviderScheme
+
+auth_scheme = GcpAuthProviderScheme(name="my-jira-auth_provider")
+mcp_toolset_jira = McpToolset(..., auth_scheme=auth_scheme)
+```