Add support for the Agents-as-Tools pattern

Author: RussellLuo

coagent/agents/react_agent/__init__.py

@@ -8,3 +8,4 @@
     ToolCallOutputItem,
     ToolCallProgressItem,
 )
+from .subagent import Subagent

coagent/agents/react_agent/agent.py

@@ -41,6 +41,7 @@
 from .messages import InputHistory, OutputMessage
 from ..model import default_model, Model
 from .converter import Converter
+from .subagent import Subagent, SubagentTool
 
 FAKE_ID = "__fake_id__"
 
@@ -98,15 +99,36 @@ def model_settings(self) -> ModelSettings:
         return self._model_settings
 
     async def started(self) -> None:
-        # Extract MCP clients from tools list
-        mcp_clients = [tool for tool in self._tools if isinstance(tool, mcputil.Client)]
+        final_tools: list[Callable] = []
 
-        # Filter out MCP clients from tools list
-        self._tools = [
-            tool for tool in self._tools if not isinstance(tool, mcputil.Client)
+        mcp_clients: list[mcputil.Client] = []
+        subagents: list[Subagent] = []
+
+        for tool in self._tools:
+            if isinstance(tool, mcputil.Client):
+                mcp_clients.append(tool)
+            elif isinstance(tool, Subagent):
+                subagents.append(tool)
+            else:
+                final_tools.append(tool)
+
+        # Load tools from MCP clients
+        mcp_tools = await self._load_mcp_tools(mcp_clients)
+        final_tools.extend(mcp_tools)
+
+        # Create tools from subagents
+        subagent_tools = [
+            SubagentTool(self, subagent).as_tool() for subagent in subagents
         ]
+        final_tools.extend(subagent_tools)
+
+        self._tools = final_tools
+
+    async def _load_mcp_tools(
+        self, mcp_clients: list[mcputil.Client]
+    ) -> list[Callable]:
+        """Load tools from all MCP clients concurrently."""
 
-        # Load tools from all MCP clients concurrently
         async def get_client_tools(client):
             try:
                 return await client.get_tools()
@@ -120,9 +142,7 @@ async def get_client_tools(client):
             *[get_client_tools(client) for client in mcp_clients]
         )
 
-        # Add all tools to the tools list
-        for mcp_tools in all_mcp_tools:
-            self._tools.extend(mcp_tools)
+        return [tool for sublist in all_mcp_tools for tool in sublist]
 
     @handler
     async def handle_history(

coagent/agents/react_agent/context.py

@@ -6,7 +6,7 @@
 
 from typing_extensions import TypeVar
 
-from .types import FunctionToolCallProgressItem, ToolCallProgressItem
+from .types import FunctionToolCallProgressItem, ToolCallProgressItem, StreamEvent
 
 TData = TypeVar("TData", default=Any)
 
@@ -41,6 +41,17 @@ def with_tool(
             tool=ToolData(name=name, call_id=call_id, arguments=arguments),
         )
 
+    @property
+    def full_tool_name(self) -> str:
+        if not self.tool:
+            return ""
+
+        name = self.tool.name
+        if self.parent and self.parent.full_tool_name:
+            name = f"{self.parent.full_tool_name}/{name}"
+
+        return name
+
     @property
     def data(self) -> TData | None:
         """Get the underlying data object."""
@@ -73,6 +84,10 @@ def report_progress(
             ),
             type="tool_call_progress_item",
         )
+        self.put_event(event)
+
+    def put_event(self, event: StreamEvent) -> None:
+        """Put an event into the event queue."""
         if self.queue:
             self.queue.put_nowait(event)