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AP46593

RAG Chat Assistant MCP Server

by AP46593

RAG Chat Assistant

A document Q&A Chat Assistant powered by Retrieval-Augmented Generation (RAG). Uses a hybrid retrieval system (semantic + keyword search) with an MCP (Model Context Protocol) server/client architecture, PII redaction, automated evaluation via RAGAS, and full observability tracing.


Architecture

Streamlit Chat UI (Client - .venv)
    ↕ MCP Protocol (Streamable HTTP on localhost:8000)
MCP Server (FastMCP - .mcpvenv)
    ├── Tools: filesystem, doc_loader, chunker, ingest, retriever
    ├── Agents: RAG Agent, Summarizer, PII Redactor, Evaluator
    ├── Storage: ChromaDB (vector) + BM25 (keyword) + Registry
    └── External: Ollama (LLM + Embeddings), Opik (Observability)

Related MCP server: Antigravity PDF MCP Server

Project Structure

L3June26_Assignment/
├── MCP_Stack/                  # MCP Server (runs in .mcpvenv)
│   ├── agents/
│   │   ├── rag_agent.py           # LangGraph RAG agent (retrieve → generate)
│   │   ├── summarizer_agent.py    # Iterative document summarization with caching
│   │   ├── pii_redactor.py        # Regex + optional LLM-based PII detection
│   │   └── evaluator_agent.py     # RAGAS evaluation + ground-truth generator
│   ├── tools/
│   │   ├── doc_loader.py          # Multi-format document loading (PDF/DOCX/TXT/CSV/XLSX/XML/images)
│   │   ├── chunker.py             # Semantic chunking with metadata
│   │   ├── ingest.py              # Ingestion pipeline + document registry
│   │   ├── retriever.py           # Hybrid search (ChromaDB + BM25 + reranking)
│   │   └── filesystem.py          # Sandboxed file browsing
│   ├── mcp_server.py              # FastMCP server entry point
│   ├── config.py                  # Server configuration
│   ├── .env.example               # Server secrets template
│   ├── requirements_mcp.txt       # Server dependencies
│   ├── knowledge_source/          # Drop documents here for ingestion
│   ├── knowledge_base/            # ChromaDB + BM25 index + registry.json (auto-generated)
│   ├── Server_Logs/               # Per-session JSONL logs
│   └── cache/                     # Summarizer cache (by content hash)
├── tests/                     # All tests
│   ├── test_property_*.py         # Property-based tests (Hypothesis)
│   ├── test_unit_*.py             # Unit tests
│   └── test_integration_*.py      # Integration tests
├── Client_Logs/               # Client JSONL logs
├── streamlit_app.py           # Streamlit chat UI (runs in .venv)
├── config.py                  # Client configuration
├── .env.example               # Client secrets template
├── requirements.txt           # Client dependencies
├── test_tools.py              # Manual test stub for tools/agents
└── README.md

Prerequisites

Dependency

Purpose

Python 3.12

Runtime (RAGAS has compatibility issues with 3.14)

uv

Package manager (replaces pip)

Ollama

Local/cloud LLM serving

Tesseract OCR (optional)

Primary OCR for images; if unavailable, falls back to gemma4:31b-cloud vision model


Setup

1. Pull Required Ollama Models

# Chat model (cloud-hosted, no local GPU needed)
ollama pull gpt-oss:120b-cloud 

# Embedding model
ollama pull nomic-embed-text

# Vision model (OCR fallback — cloud-hosted, no local GPU needed)
ollama pull gemma4:31b-cloud

2. Create Virtual Environments

MCP Server (.mcpvenv):

uv venv .mcpvenv --python 3.12

# Windows
.mcpvenv\Scripts\activate

# Linux/macOS
source .mcpvenv/bin/activate

uv pip install -r MCP_Stack/requirements_mcp.txt

Streamlit Client (.venv):

uv venv .venv --python 3.12

# Windows
.venv\Scripts\activate

# Linux/macOS
source .venv/bin/activate

uv pip install -r requirements.txt

3. Configure Environment Variables

# Copy templates
cp .env.example .env
cp MCP_Stack/.env.example MCP_Stack/.env

Edit each .env file with your actual values:

Client .env:

OLLAMA_BASE_URL=http://localhost:11434
ORCHESTRATOR_MODEL=gpt-oss:120b-cloud
MCP_SERVER_URL=http://localhost:8000/mcp
ENABLE_OPIK_TRACING=false
OPIK_API_KEY=<your-key>
OPIK_WORKSPACE=<your-workspace>
OPIK_PROJECT_NAME=rag-chat-assistant

Server MCP_Stack/.env:

OLLAMA_BASE_URL=http://localhost:11434
DEFAULT_MODEL=gpt-oss:120b-cloud
EMBEDDING_MODEL=nomic-embed-text
VISION_MODEL=gemma4:31b-cloud
CHUNK_SIZE=2000
CHUNK_OVERLAP=200
RETRIEVAL_TOP_K=5
SEMANTIC_WEIGHT=0.7
PII_USE_LLM=false
ENABLE_RAGAS_EVAL=false
MCP_SERVER_PORT=8000

4. Add Documents to Knowledge Source

Place your documents (PDF, DOCX, TXT, CSV, XLSX, XML, or images) into:

MCP_Stack/knowledge_source/

These will be automatically ingested when the MCP server starts.


Running the Application

Step 1: Start the MCP Server

Open a terminal and activate the server environment:

# Windows
.mcpvenv\Scripts\activate

# Linux/macOS
source .mcpvenv/bin/activate

# Start the server
python -m MCP_Stack.mcp_server

On startup, the server will:

  1. Inject SSL certificates (truststore)

  2. Load existing knowledge base from disk

  3. Scan knowledge_source/ and ingest any new or modified documents

  4. Skip unchanged documents (based on content hash)

  5. Register all tools and agents

  6. Serve MCP protocol on http://localhost:8000/mcp

Note: Documents added to knowledge_source/ while the server is running will NOT be auto-detected. Restart the server to ingest new files.

Step 2: Start the Streamlit Client

Open a separate terminal and activate the client environment:

# Windows
.venv\Scripts\activate

# Linux/macOS
source .venv/bin/activate

# Start the UI
streamlit run streamlit_app.py

The chat UI will open in your browser (typically at http://localhost:8501).


Usage

Asking Questions

Type your question in the chat input. The RAG agent will:

  1. Search the knowledge base using hybrid retrieval (semantic + keyword)

  2. Generate an answer with citations to source documents

  3. Display RAGAS evaluation scores (if enabled)

Document Management

Through the chat interface you can:

  • Browse files — list and inspect documents in knowledge_source/

  • Ingest manually — force re-ingest of a specific file or all files

  • List documents — see all ingested documents with metadata

  • Delete documents — remove a document from the knowledge base

  • Summarize — get a concise summary of a long document

Ground-Truth Test Data Generation

Generate evaluation test data from your documents:

  1. Provide a document name from knowledge_source/

  2. The system generates question-answer pairs with context passages

  3. Output is saved as JSON for use with RAGAS evaluation (faithfulness, answer relevancy, context precision, context recall)


Configuration Reference

Server Configuration (MCP_Stack/config.py)

Parameter

Default

Description

OLLAMA_BASE_URL

http://localhost:11434

Ollama API endpoint

DEFAULT_MODEL

gpt-oss:120b-cloud

Chat model for answer generation

EMBEDDING_MODEL

nomic-embed-text

Embedding model for vector search

VISION_MODEL

gemma4:31b-cloud

Cloud vision model (OCR fallback)

MAX_TOKENS

2048

Max tokens for generated responses

TEMPERATURE

0.7

LLM temperature

CHUNK_SIZE

2000

Characters per chunk (~500 tokens)

CHUNK_OVERLAP

200

Overlap between consecutive chunks

RETRIEVAL_TOP_K

5

Number of chunks to retrieve

SEMANTIC_WEIGHT

0.7

Semantic vs keyword balance (0.7 = 70% semantic)

PII_USE_LLM

false

Enable LLM-based PII detection (slower, catches more)

ENABLE_RAGAS_EVAL

false

Auto-evaluate responses with RAGAS

MCP_SERVER_PORT

8000

Server port

Client Configuration (config.py)

Parameter

Default

Description

OLLAMA_BASE_URL

http://localhost:11434

Ollama API endpoint

ORCHESTRATOR_MODEL

gpt-oss:120b-cloud

Model for client-side orchestration

MCP_SERVER_URL

http://localhost:8000/mcp

MCP server endpoint

ENABLE_OPIK_TRACING

false

Enable Opik observability tracing


Running Tests

# Activate the server environment (has all dependencies)
# Windows
.mcpvenv\Scripts\activate

# Linux/macOS
source .mcpvenv/bin/activate

# Run all tests
python -m pytest tests/ -v

# Run only property-based tests
python -m pytest tests/test_property_*.py -v

# Run only unit tests
python -m pytest tests/test_unit_*.py -v

# Run a specific test file
python -m pytest tests/test_unit_chunker.py -v

Key Design Decisions

Decision

Choice

Rationale

Protocol

MCP over Streamable HTTP

Standardized tool/agent interface; single endpoint

Agent Framework

LangGraph

Stateful graph workflows with conditional routing

Vector Store

ChromaDB (persistent)

Local file-based; no external service needed

Keyword Search

rank-bm25 (BM25Okapi)

Lightweight in-process; complements semantic search

Embedding

nomic-embed-text via Ollama

Dedicated embedding model; local inference

OCR

Tesseract → gemma4:31b-cloud fallback

Tesseract is fast; cloud vision is available everywhere

Observability

Opik (by Comet)

Native LangChain callback integration

Evaluation

RAGAS

Standard RAG evaluation framework

SSL

truststore

Corporate proxy support via Windows cert store


Troubleshooting

Issue

Solution

SSL errors behind corporate proxy

Ensure truststore is installed and imported first in entry points

Ollama connection refused

Verify Ollama is running: ollama list

Empty OCR results

Install Tesseract, or ensure gemma4:31b-cloud is available via ollama pull gemma4:31b-cloud

MCP connection timeout

Check that the server is running on the configured port (default 8000)

Documents not appearing after adding

Restart the MCP server — ingestion only happens at startup

RAGAS scores not showing

Set ENABLE_RAGAS_EVAL=true in MCP_Stack/.env


Supported Document Formats

Format

Extensions

Method

PDF

.pdf

pypdf + pdfplumber fallback

Word

.docx

python-docx

Plain Text

.txt

Direct read with encoding detection

CSV

.csv

pandas

Excel

.xlsx

openpyxl via pandas

XML

.xml

xml.etree + lxml fallback

Images

.png, .jpg, .jpeg, .tiff

Tesseract OCR → gemma4:31b-cloud fallback

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Maintainers
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Release cycle
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Commit activity

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