Building managed agents

Managed agents on the Gemini API let you extend the Antigravity agent with your own instructions, skills, and data. You can customize the agent inline at interaction time, or save the configuration as a managed agent you invoke by ID.

Customize the Antigravity agent

The fastest way to build a custom agent is to pass your configuration inline while creating a new interaction with no registration step required. You can extend the agent in several key ways:

  • Model selection: Choose the underlying Gemini model via agent_config (defaults to Gemini 3.7 Flash).
  • System instructions: Pass inline text via system_instruction to shape behavior.
  • Tools: Override default tools (Code Execution, Search, URL Context), register remote MCP servers, or define custom functions (Function Calling).
  • Files and skills: Mount files like AGENTS.md and SKILL.md into the environment.

Here is an example of passing all three inline:

Python