ReplyMate
LangGraph-Based AI Communication Agent for Second-Language English Speakers
Year:
2025
Role:
Founder · Architect · Program Lead
Stack:
LangGraph · MCP · OpenAI Whisper · Gmail · Outlook · LinkedIn · Slack
Type:
AI Agents · Web App
ReplyMate is an AI communication assistant built for second-language English speakers — helping users draft, refine, and send professional messages across email, LinkedIn, Slack, and calendar platforms. What started as a simple writing tool evolved into a full LangGraph-based multi-agent system with MCP integrations across five platforms.
As the sole architect and program lead, I defined the system architecture, managed cross-platform integration dependencies, made key product decisions including a BYOK (Bring Your Own Key) model to reduce deployment risk, and produced a full technical whitepaper targeting deployment at replymate.chenruolan.com.
System Architecture
The agent orchestration layer is built on LangGraph, coordinating specialized sub-agents for tone adjustment, context retrieval, and platform-specific formatting. MCP servers handle authenticated connections to Gmail, Outlook, LinkedIn, Slack/Teams, and calendar platforms — keeping credentials local via the BYOK architecture.
Key Program Decisions
BYOK Architecture
Instead of a centralized API key model, users bring their own keys — eliminating credential risk and simplifying compliance. This decision unblocked the enterprise use case and reduced deployment friction.
LangGraph over LangChain
Chose LangGraph for stateful, cyclical agent workflows — enabling the system to retry, re-route, and maintain context across multi-turn conversations rather than one-shot completions.
Classroom Mode
Designed a specialized mode for academic writing, with stricter tone constraints and citation-aware suggestions — expanding the target user to students and researchers.
Lecture Notes via Whisper
Integrated OpenAI Whisper for audio-to-notes, allowing the agent to process lecture recordings and generate structured summaries directly within the workflow.
Platform Integrations
Managed integration dependencies across 5 external platforms, each with distinct authentication flows and API constraints:
📧 Email
Gmail · Outlook
OAuth2 flows, threading context, draft management
💼 Professional
LinkedIn
Message tone calibration, connection context awareness
📅 Productivity
Slack · Teams · Calendar
Real-time messaging, scheduling intent detection