common_configs.py

# Copyright 2026 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
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"""Common configuration classes for agent YAML configs."""

from __future__ import annotations

from typing import Any
from typing import List
from typing import Optional

from pydantic import BaseModel
from pydantic import ConfigDict
from pydantic import model_validator

from ..features import experimental
from ..features import FeatureName


@experimental(FeatureName.AGENT_CONFIG)
class ArgumentConfig(BaseModel):
  """An argument passed to a function or a class's constructor."""

  model_config = ConfigDict(extra="forbid")

  name: Optional[str] = None
  """Optional. The argument name.

  When the argument is for a positional argument, this can be omitted.
  """

  value: Any
  """The argument value."""


@experimental(FeatureName.AGENT_CONFIG)
class CodeConfig(BaseModel):
  """Code reference config for a variable, a function, or a class.

  This config is used for configuring callbacks and tools.
  """

  model_config = ConfigDict(extra="forbid")

  name: str
  """Required. The name of the variable, function, class, etc. in code.

  Examples:

    When used for tools,
      - It can be ADK built-in tools, such as `google_search` and `AgentTool`.
      - It can also be users' custom tools, e.g. my_library.my_tools.my_tool.

    When used for callbacks, it refers to a function, e.g. `my_library.my_callbacks.my_callback`
  """

  args: Optional[List[ArgumentConfig]] = None
  """Optional. The arguments for the code when `name` refers to a function or a
  class's constructor.

  Examples:
    ```
    tools
      - name: AgentTool
        args:
          - name: agent
            value: search_agent.yaml
          - name: skip_summarization
            value: True
    ```
  """


@experimental(FeatureName.AGENT_CONFIG)
class AgentRefConfig(BaseModel):
  """The config for the reference to another agent."""

  model_config = ConfigDict(extra="forbid")

  config_path: Optional[str] = None
  """The YAML config file path of the sub-agent.

  Only one of `config_path` or `code` can be set.

  Example:

    ```
    sub_agents:
      - config_path: search_agent.yaml
      - config_path: my_library/my_custom_agent.yaml
    ```
  """

  code: Optional[str] = None
  """The agent instance defined in the code.

  Only one of `config` or `code` can be set.

  Example:

    For the following agent defined in Python code:

    ```
    # my_library/custom_agents.py
    from google.adk.agents.llm_agent import LlmAgent

    my_custom_agent = LlmAgent(
        name="my_custom_agent",
        instruction="You are a helpful custom agent.",
        model="gemini-2.5-flash",
    )
    ```

    The yaml config should be:

    ```
    sub_agents:
      - code: my_library.custom_agents.my_custom_agent
    ```
    """

  @model_validator(mode="after")
  def validate_exactly_one_field(self) -> AgentRefConfig:
    code_provided = self.code is not None
    config_path_provided = self.config_path is not None

    if code_provided and config_path_provided:
      raise ValueError("Only one of `code` or `config_path` should be provided")
    if not code_provided and not config_path_provided:
      raise ValueError(
          "Exactly one of `code` or `config_path` must be provided"
      )

    return self