FastAPI AgentRouter

Simplified AI Agent integration for FastAPI with Slack support.

Features

• 🚀 Simple Integration - Just 2 lines to add agent to your FastAPI app
• 🤖 Vertex AI Support - Native support for Google's Vertex AI Agent Builder
• 💬 Slack Integration - Built-in Slack Bolt integration
• 🎯 Protocol-Based - Works with any agent implementing the AgentProtocol
• ⚡ Async & Streaming - Full async support with streaming responses
• 🧩 Dependency Injection - Leverage FastAPI's DI system
• 📁 Modular Architecture - Clean separation of concerns

Installation

# Basic installation
pip install fastapi-agentrouter

# With Slack support
pip install "fastapi-agentrouter[slack]"

# With Vertex AI ADK support
pip install "fastapi-agentrouter[vertexai]"

# All extras
pip install "fastapi-agentrouter[all]"

Quick Start

With Vertex AI Agent Builder

from fastapi import FastAPI
import fastapi_agentrouter

app = FastAPI()

# Two-line integration!
app.dependency_overrides[fastapi_agentrouter.get_agent] = (
    fastapi_agentrouter.get_vertex_ai_agent_engine
)
app.include_router(fastapi_agentrouter.router)

With Custom Agent Implementation

from fastapi import FastAPI
from fastapi_agentrouter import router, get_agent, AgentProtocol

# Your agent implementation
class MyAgent:
    def create_session(self, *, user_id=None, **kwargs):
        return {"id": "session-123"}

    def list_sessions(self, *, user_id=None, **kwargs):
        return {"sessions": []}

    def stream_query(self, *, message: str, user_id=None, session_id=None, **kwargs):
        # Process the message and yield responses
        yield {"content": f"Response to: {message}"}

app = FastAPI()

# Two-line integration!
app.dependency_overrides[get_agent] = lambda: MyAgent()
app.include_router(router)

That's it! Your agent is now available at:

• /agent/slack/events - Handle all Slack events and interactions (when Slack is configured)

Configuration

Vertex AI Configuration

When using Vertex AI Agent Builder, configure these environment variables:

# Required for Vertex AI
export VERTEXAI__PROJECT_ID="your-project-id"
export VERTEXAI__LOCATION="us-central1"
export VERTEXAI__STAGING_BUCKET="your-staging-bucket"
export VERTEXAI__AGENT_NAME="your-agent-name"

The library automatically warms up the agent engine during router initialization to ensure fast response times.

Slack Configuration

To enable Slack integration, set these environment variables:

# Required for Slack integration
export SLACK__BOT_TOKEN="xoxb-your-bot-token"
export SLACK__SIGNING_SECRET="your-signing-secret"

Note: Slack integration is only enabled when both SLACK__BOT_TOKEN and SLACK__SIGNING_SECRET are configured. If not set, Slack endpoints will return 404.

Slack Setup

1. Create a Slack App at https://api.slack.com/apps
2. Get your Bot Token and Signing Secret from Basic Information
3. Set environment variables:

   export SLACK__BOT_TOKEN="xoxb-your-bot-token"
   export SLACK__SIGNING_SECRET="your-signing-secret"
   

4. Configure Event Subscriptions URL: https://your-domain.com/agent/slack/events
5. Subscribe to bot events:
   • app_mention - When your bot is mentioned
   • message.im - Direct messages to your bot (optional)
6. For interactive components and slash commands, use the same URL: https://your-domain.com/agent/slack/events

Agent Protocol

Your agent must implement the AgentProtocol interface with these methods:

from typing import Any, Generator

class AgentProtocol:
    def create_session(
        self,
        *,
        user_id: str | None = None,
        **kwargs: Any,
    ) -> dict[str, Any]:
        """Create a new session for the agent.

        Returns a dictionary containing at least the session 'id'.
        """
        ...

    def list_sessions(
        self,
        *,
        user_id: str | None = None,
        **kwargs: Any,
    ) -> dict[str, Any]:
        """List sessions for a given user.

        Returns a dictionary with a 'sessions' key containing a list of
        session dictionaries.
        """
        ...

    def stream_query(
        self,
        *,
        message: str,
        user_id: str | None = None,
        session_id: str | None = None,
        **kwargs: Any
    ) -> Generator[dict[str, Any], Any, None]:
        """Stream responses from the agent."""
        ...

The stream_query method should yield response events as dictionaries.

API Reference

Core Components

fastapi_agentrouter.router

Pre-configured APIRouter with automatic agent integration:

• /agent/slack/events - Slack event handler (when Slack is configured)

fastapi_agentrouter.get_agent

Dependency function that should be overridden with your agent:

app.dependency_overrides[fastapi_agentrouter.get_agent] = your_get_agent_function

fastapi_agentrouter.get_vertex_ai_agent_engine

Pre-configured function to get Vertex AI Agent Engine:

app.dependency_overrides[fastapi_agentrouter.get_agent] = (
    fastapi_agentrouter.get_vertex_ai_agent_engine
)

fastapi_agentrouter.AgentProtocol

Protocol class that defines the interface for agents.

fastapi_agentrouter.Settings

Pydantic settings class for configuration management.

Environment Variables

The library uses pydantic-settings for configuration management:

Slack Configuration:

• SLACK__BOT_TOKEN - Slack Bot User OAuth Token
• SLACK__SIGNING_SECRET - Slack Signing Secret

Vertex AI Configuration:

• VERTEXAI__PROJECT_ID - GCP Project ID
• VERTEXAI__LOCATION - GCP Location (e.g., us-central1)
• VERTEXAI__STAGING_BUCKET - GCS Bucket for staging
• VERTEXAI__AGENT_NAME - Display name of the Vertex AI Agent

Examples

See the examples directory for complete examples:

• basic_usage.py - Basic Vertex AI integration example

Docker

Docker images are available on Docker Hub:

# Pull the latest image
docker pull chanyou0311/fastapi-agentrouter:latest

# Run with environment variables
docker run -p 8000:8000 \
  -e VERTEXAI__PROJECT_ID=your-project-id \
  -e VERTEXAI__LOCATION=us-central1 \
  -e VERTEXAI__STAGING_BUCKET=your-bucket \
  -e VERTEXAI__AGENT_NAME=your-agent-name \
  chanyou0311/fastapi-agentrouter:latest

Development

Setup Development Environment

# Clone the repository
git clone https://github.com/chanyou0311/fastapi-agentrouter.git
cd fastapi-agentrouter

# Install with uv (recommended)
uv sync --all-extras --dev

# Or with pip
pip install -e ".[all,dev,docs]"

# Install pre-commit hooks
pre-commit install

Run Tests

# Run all tests
pytest

# Run with coverage
pytest --cov=src --cov-report=html

# Run specific tests
pytest tests/test_router.py

Build Documentation

# Serve docs locally
mkdocs serve

# Build docs
mkdocs build

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

1. Fork the repository
2. Create your feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add some amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

License

This project is licensed under the MIT License - see the LICENSE file for details.

Links

• Documentation
• PyPI Package
• Docker Hub
• GitHub Repository
• Issue Tracker