🧬 ChemLint

ChemLint — An MCP server that gives LLMs native access to cheminformatics and molecular ML tools

Summary

ChemLint transforms AI assistants into powerful molecular machine learning workbenches. Through the Model Context Protocol (MCP), LLMs gain the ability to manipulate molecular structures, calculate descriptors, train ML models, and generate comprehensive analysis reports — all through natural conversation.

Simply chat with Claude Desktop (or any MCP client) to perform complex cheminformatics workflows that would normally require writing Python scripts and juggling multiple libraries.

✨ Key Features

🧪 Molecular Operations

• SMILES Processing: Standardization, canonicalization, validation, 10-step cleaning pipelines
• Molecular Descriptors: Simple (MW, LogP, TPSA) and complex (ECFP, MACCS, RDKit fingerprints)
• Scaffold Analysis: Bemis-Murcko, generic scaffolds, cyclic skeletons with diversity metrics
• Similarity & Clustering: Tanimoto similarity, DBSCAN, hierarchical, k-means, Butina clustering
• Substructure Matching: SMARTS pattern detection with 88+ built-in functional groups

🤖 Machine Learning

• 33 ML Algorithms: Classification & regression (RF, GBM, SVM, linear models, ensembles with uncertainty)
• Cross-Validation: 6 strategies (k-fold, stratified, Monte Carlo, scaffold, cluster, leave-P-out)
• Hyperparameter Tuning: Grid search, random search with customizable parameter spaces
• Model Evaluation: 20+ metrics, confusion matrices, ROC curves, calibration plots

📊 Quality Reports

• Data Quality Analysis: 19-section comprehensive report (PAINS, Lipinski, duplicates, stereochemistry, etc.)
• Split Quality Analysis: 8 data leakage checks (duplicates, similarity, scaffolds, stereoisomers)
• Scaffold Reports: Diversity metrics (Gini, Shannon entropy), enrichment analysis, structural outliers

📈 Visualization & Statistics

• Interactive Plots: Scatter plots with molecular tooltips, histograms, density plots, box plots, heatmaps
• Statistical Tests: 15+ tests (t-test, ANOVA, Mann-Whitney, Kruskal-Wallis, chi-square, normality tests)
• Dimensionality Reduction: PCA, t-SNE for chemical space visualization
• Outlier Detection: Z-score, IQR, isolation forest, local outlier factor

🔬 Advanced Features

• Activity Cliff Detection: Find structurally similar molecules with large activity differences
• Data Splitting: Random, stratified, scaffold-based, cluster-based, temporal splits
• Duplicate Handling: Activity conflict detection with aggregation strategies
• Drug-Likeness Filters: Lipinski, Veber, PAINS, QED, lead-likeness, rule of three

💬 Example Prompts

Getting Started

"Create a new project and import dataset from /path/to/molecules.csv"

"Show me the summary statistics"

"What columns do I have and what are their data types?"

"What are the steps I need to perform to train a robust ML model on this data?"

Data Quality & Cleaning

"Run a comprehensive data quality report on my dataset"

"Standardize all SMILES strings using the default protocol"

"Find and handle duplicate molecules - some might have conflicting labels"

"Remove PAINS patterns and filter by Lipinski's Rule of Five"

Molecular Properties & Features

"Calculate molecular weight, logP, TPSA, and number of H-bond donors/acceptors"

"Generate Morgan fingerprints with radius 2"

"Extract Bemis-Murcko scaffolds and analyze the diversity"

"Add columns for all functional groups present in each molecule"

Visualization and Statistical Analysis

"Make scatter plot of molecular weight vs logP colored by activity"

"Create a t-SNE visualization colored by pKi"

"Make a correlation heatmap for MW, LogP, TPSA, HBD, HBA, and pKi"

"Box plot of molecular weight for actives vs inactives. Is there a statistical difference?"

"Test if my pKi values are normally distributed"

"Are there any MW outliers in my data?"

Similarity & Clustering

"Find the 10 most similar molecules to this SMILES: CC(=O)Oc1ccccc1C(=O)O"

"Cluster my molecules using DBSCAN and visualize the clusters"

"Which test molecules are most similar to my training set?"

"Are there any activity cliffs in my data?"

Machine Learning Workflows

"Split my data using scaffold-based splitting 80/20 train/test"

"Check the quality of my train/test split for any data leakage issues"

"Train a Random Forest classifier with 5-fold cross-validation"

"Tune hyperparameters for a gradient boosting model using grid search"

"Evaluate my model on the test set and show me accuracy, precision, recall, and F1"

"Make predictions on the molecules in /path/to/dataset.csv and show uncertainty estimates"

End-to-End Example

"Train a ML model for bioactivity prediction using /path/to/dataset.csv"

"Import this dataset /path/to/dataset.csv, standardize SMILES, remove duplicates, 
filter by Lipinski rule of five, calculate ECFP4 fingerprints, do a scaffold-based 
80/20 split, train a Random Forest with cross-validation, evaluate on the test set."

"Use this dataset /path/to/dataset.csv to create a robust model for virtual screening 
for the molecules in /path/to/virtual_screening.csv"

🚀 Installation

Prerequisites

• Python 3.13+ (included with uv)
• uv - Fast Python package installer (install instructions)

  # macOS/Linux
  curl -LsSf https://astral.sh/uv/install.sh | sh
  
  # Or with pip
  pip install uv
  

• Cairo (optional) - Only needed for plotting of ACS-style molecular structures

  # macOS
  brew install cairo
  
  # Linux
  sudo apt-get install libcairo2-dev  # Ubuntu/Debian
  sudo yum install cairo-devel        # RHEL/CentOS
  

Quick Install for Claude Desktop (Recommended)

Simply run the installer script - it handles installation, configuration, and deployment:

# Clone repository
git clone https://github.com/derekvantilborg/ChemLint.git
cd ChemLint

# Run installer (installs AND configures Claude Desktop)
./install.sh

The installer will:

• ✅ Detect and verify uv installation
• ✅ Install Python dependencies
• ✅ Run server tests
• ✅ Detect Cairo (optional, for high-quality molecular images - will warn if missing)
• ✅ Automatically configure Claude Desktop
• ✅ Deploy the server to Claude

After installation, restart Claude Desktop:

# macOS
pkill -x Claude && sleep 1 && open -a Claude

# Linux/Windows
# Restart Claude Desktop from your applications menu

Manual Installation

If you prefer manual setup or use a different MCP client:

# 1. Clone and install dependencies
git clone https://github.com/derekvantilborg/ChemLint.git
cd ChemLint
uv sync

# 2. Run tests to verify installation
uv run pytest -m server -q

For Claude Desktop users: Run the configuration script to deploy:

./mcp_client_configs/configure_claude.sh $(which uv) $(pwd) [cairo_path]

Other MCP Clients

For clients other than Claude Desktop, add this to your MCP client configuration:

{
  "mcpServers": {
    "chemlint": {
      "command": "/path/to/uv",
      "args": [
        "run",
        "--with",
        "mcp[cli]",
        "--directory",
        "/path/to/ChemLint",
        "mcp",
        "run",
        "./src/chemlint/server.py"
      ],
      "enabled": true
    }
  }
}

🏗️ Architecture

Core Components

molml_mcp/
├── tools/                      # 150+ molecular ML tools
│   ├── cleaning/              # SMILES cleaning, deduplication, label processing
│   ├── core/                  # Dataset ops, filtering, outliers, statistics, dim reduction
│   ├── core_mol/              # Scaffolds, similarity, activity cliffs, complexity
│   ├── featurization/         # Descriptors (simple, complex, SMILES encoding)
│   ├── ml/                    # Training, evaluation, CV, hyperparameter tuning
│   ├── plotting/              # Interactive visualizations (scatter, histogram, heatmaps)
│   └── reports/               # Quality, scaffold, and split analysis reports
├── infrastructure/
│   ├── resources.py           # Manifest-based resource tracking
│   └── supported_resource_types.py  # CSV, model, JSON, PNG handlers
└── server.py                  # FastMCP server registration

Resource Management & Traceability

All data operations use a manifest-based tracking system that functions like a digital lab journal, providing complete traceability of your molecular ML workflow:

How it works:

• Unique IDs: Every file gets a unique identifier {filename}_{8_HEX_ID}.{ext} (e.g., cleaned_data_A3F2B1D4.csv)
• Manifest JSON: A manifest.json file in your project directory logs every operation with:
  • Timestamp: When the resource was created
  • Function: Which tool generated it (e.g., standardize_smiles_dataset)
  • Explanation: Human-readable description of what was done
  • Lineage: Input filename (if applicable), creating a traceable chain

Example manifest entry:

{
  "cleaned_molecules_A3F2B1D4.csv": {
    "type": "csv",
    "created_at": "2026-01-20T14:23:45.123456",
    "created_by": "standardize_smiles_dataset",
    "explanation": "Standardized SMILES with salt removal and neutralization"
  }
}

Benefits:

• 📋 Full Audit Trail: Know exactly what operations were performed and when
• 🔄 Reproducibility: Recreate your entire pipeline from the manifest log
• 🔍 Debugging: Trace back through processing steps when investigating issues
• 👥 Collaboration: Share projects with complete operation history
• Type Registry: Handlers for CSV (pandas), models (joblib), JSON, PNG (matplotlib)
• Project Isolation: Each project has its own manifest and resource directory

Tool Categories

150+ tools organized by domain:

1. Data Management (15 tools): Import, export, merge, subset, inspect, filter datasets
2. Molecular Cleaning (10 tools): SMILES standardization, salt removal, deduplication
3. Descriptors (12 tools): Simple properties, fingerprints, encoding methods
4. Scaffolds (8 tools): Bemis-Murcko, generic, diversity analysis
5. Similarity (6 tools): Pairwise matrices, k-NN, training set similarity
6. Clustering (5 tools): DBSCAN, hierarchical, k-means, Butina
7. Machine Learning (40 tools): Training, CV, tuning, evaluation, metrics
8. Statistics (15 tools): t-tests, ANOVA, correlation, normality tests
9. Visualization (8 tools): Scatter, histogram, density, box, heatmap plots
10. Quality Reports (5 tools): Data quality, split quality, scaffold analysis
11. Activity Cliffs (4 tools): Cliff detection for classification/regression
12. Outlier Detection (6 tools): Z-score, IQR, isolation forest, LOF
13. Dimensionality Reduction (2 tools): PCA, t-SNE

🧪 Testing

# Run all tests (363 tests)
uv run pytest -v

# Run specific test modules
uv run pytest tests/tools/ml/test_training.py -v
uv run pytest tests/tools/reports/test_quality.py -v

# Run server initialization test
uv run pytest -m server -v

# Run with coverage
uv run pytest --cov=chemlint --cov-report=html

Test Coverage:

• ✅ 363 tests across all modules
• ✅ Infrastructure (resource management, manifests)
• ✅ Cleaning & filtering tools
• ✅ Molecular operations (scaffolds, similarity, activity cliffs)
• ✅ ML training, evaluation, and cross-validation
• ✅ Report generation (quality, scaffold, split analysis)
• ✅ Visualization and statistical analysis

📄 License

MIT License - see LICENSE file for details.

This project is open source and free to use for academic and commercial purposes.

🙏 Acknowledgments

Built with:

• FastMCP - Model Context Protocol server framework
• RDKit - Cheminformatics and machine learning toolkit
• scikit-learn - Machine learning library
• pandas - Data manipulation and analysis
• NumPy - Numerical computing
• Plotly & Dash - Interactive visualizations
• uv - Fast Python package manager

Special thanks to the RDKit community for maintaining the foundational cheminformatics toolkit

✍️ Cite

If you use ChemLint in your research, please cite our work:

van Tilborg, D., & Grisoni, F. (2026). ChemLint: Conversational Cheminformatics with Large Language Models. ChemRxiv. https://doi.org/10.26434/chemrxiv.15000386

The preprint is available on ChemRxiv.

BibTeX

@article{vanTilborg2026chemlint,
  title   = {{ChemLint}: Conversational Cheminformatics with Large Language Models},
  author  = {van Tilborg, Derek and Grisoni, Francesca},
  year    = {2026},
  journal = {ChemRxiv},
  doi     = {10.26434/chemrxiv.15000386},
  url     = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15000386/v1}
}

📬 Contact

Derek van Tilborg - @derekvantilborg

Project Link: https://github.com/molML/ChemLint

Issues & Feature Requests: GitHub Issues