ChunkTuner
Integrates with OpenAI's embedding models to evaluate and score chunking strategies.
chunktuner
Auto chunking tuner and MCP server for RAG pipelines.
Give it your documents. It tries multiple chunking strategies, measures which one lets an AI answer questions most accurately, and tells you the winner.
What it does
When building a RAG pipeline, how you split documents into chunks directly impacts retrieval quality. chunktuner automates the process of finding the optimal chunking strategy for your specific corpus, embedding model, and use case.
It benchmarks strategies like fixed-token windows, recursive character splitting, semantic splitting, PDF structural chunking, and AST-based code chunking — then scores each one against real retrieval metrics (token recall, MRR, NDCG) and optional generation metrics (RAGAS faithfulness, answer relevancy).
Interfaces
Python library — programmatic integration into your pipeline
CLI (
chunk-tune) — human-driven tuning from the terminalMCP server — use directly from Claude Desktop or any MCP host
Quickstart
# Install
uv tool install chunktuner
# Initialize workspace
chunk-tune init --provider openai
# See cost estimate before running anything
chunk-tune estimate ./my_docs --use-case rag_qa
# Get a recommendation
chunk-tune recommend ./my_docs --use-case rag_qaPython API:
from pathlib import Path
from chunktuner import FileIngestor, LiteLLMEmbeddingFunction, AutoTuner
from chunktuner import default_registry, Evaluator, ScoreCalculator
docs = FileIngestor().ingest_dir(Path("./my_docs"))
embedding_fn = LiteLLMEmbeddingFunction("text-embedding-3-small")
tuner = AutoTuner(
strategies=default_registry,
evaluator=Evaluator(embedding_fn),
scorer=ScoreCalculator(use_case="rag_qa"),
)
result = tuner.recommend(docs, use_case="rag_qa")
print(result.best.config)Supported strategies
Strategy | Best for |
| Baseline; uniform token windows |
| General prose and documentation |
| Theme-heavy articles |
| Structured Markdown docs |
| PDFs with layout regions and tables |
| PDF/DOCX with mixed layout and text |
| Long docs with dense cross-references |
| High-value narrative documents |
| Code repos (Python, JavaScript) |
| Code baseline (sliding window) |
MCP server (Claude Desktop)
Python FastMCP (chunk-tune-mcp, stdio). No Node.js build. See docs/mcp_setup.md.
Add to your .mcp.json:
{
"mcpServers": {
"chunktuner": {
"command": "uvx",
"args": ["--from", "chunktuner[mcp]", "chunk-tune-mcp"],
"env": {
"CHUNK_TUNER_BASE_DIR": "/path/to/your/corpus"
}
}
}
}Tools available: list_strategies, preview_chunks, evaluate_chunking, recommend_config.
CLI reference
chunk-tune init Bootstrap workspace config
chunk-tune analyze Quick structural scan (no API cost)
chunk-tune estimate Dry-run cost/token estimate
chunk-tune evaluate Full evaluation across strategies
chunk-tune recommend Evaluation + best config recommendation
chunk-tune compare Side-by-side comparison of specific strategies
chunk-tune preview Inspect how a strategy splits a document
chunk-tune cache Manage embedding and chunk cacheInstallation options
uv add chunktuner # library
uv tool install chunktuner # global CLI
uvx chunktuner # ephemeral, no install
# With optional extras
uv add "chunktuner[docling]" # PDF/DOCX support
uv add "chunktuner[ragas]" # generation metrics
uv add "chunktuner[semantic]" # semantic chunking
uv add "chunktuner[code]" # AST code chunking
uv add "chunktuner[all]" # everythingContributing
See CONTRIBUTING.md.
👨🏻💻 Author
Full stack developer with experience in building E2E AI applications.
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