Summary
Semantic codebase indexing that turns 19 tool calls into one. Built on tree-sitter parsing and TF-IDF clustering, it extracts domain concepts, naming conventions, and behavioral similarity from Python, TypeScript, JavaScript, and Rust repos. Query concepts across a project with `query_concept` and `locate_concept`, check identifier naming with `check_naming`, trace type flows with `trace_type`, or find behaviorally similar functions using CodeRankEmbed embeddings via `find_similar_logic`. The index runs locally with no API keys and includes `ontology_diff` for tracking vocabulary changes across git refs. Most useful when onboarding to large codebases or enforcing naming consistency across teams. Requires a git repository and auto-indexes on first run.
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ontomics
ontomics gives any coding agent instant knowledge of your codebase. One tool call instead of 19. ~20x fewer tokens.
https://github.com/user-attachments/assets/01afa8a0-1bc2-4686-94d7-965fef7610c3
Visualization for the voxelmorph project -- a library for unsupervised learning in image registration
Benchmark
Tested with Claude Sonnet — same question, with and without ontomics.
"What does 'transform' mean in this codebase?" on voxelmorph (full transcript):
| With ontomics | Without | |
|---|---|---|
| Tool calls | 1 | 19 |
| Tokens | ~3.7k | ~76k |
| Time | 5s | 1m 15s |
| Answer quality | Complete | Complete |
"What are the main domain concepts in this codebase?" on ScribblePrompt (full transcript):
| With ontomics | Without | |
|---|---|---|
| Tool calls | 1 | 26 |
| Tokens | ~3.7k | ~61.6k |
| Time | ~5s | 56s |
| Answer quality | Complete | Complete |
Both conditions produced complete, correct answers. ontomics got there in one call.
What it does that search can't
Search tells you where a string appears. An LSP tells you where a symbol is defined and referenced. Neither answers: what are the domain concepts in this codebase? How do they relate? What naming conventions emerged? What changed in the domain vocabulary since last release? Which functions behave similarly, regardless of what they're named?
ontomics builds a semantic index of your project's domain — clustering related symbols into concepts, detecting naming conventions from usage frequency, resolving abbreviations, grouping functions by behavioral similarity, and tracking how the vocabulary evolves over time. That index can be exported as a portable artifact to bootstrap conventions in other repos.
Behavioral similarity
Beyond naming and concepts, ontomics embeds raw function bodies using CodeRankEmbed (768-dim, contrastive code retrieval) and clusters them by behavioral similarity. This surfaces relationships that neither naming nor call graphs expose:
❯ What functions behave like spatial_transform()?
random_transform() nn/functional.py:352 0.80
spatial_transform() functional.py:596 0.69
random_transform() functional.py:1399 0.67
random_disp() nn/functional.py:275 0.65
integrate_disp() functional.py:764 0.65
compose() nn/functional.py:216 0.63
disp_to_trf() functional.py:343 0.62
The result also reveals that random_transform appears at two locations with different similarity scores — a sign of implementation duplication that concept-level search would miss entirely.
Install
Install once, available in every project. No configuration needed — ontomics auto-detects the repo and indexes it on first run.
ontomics requires a git repository (.git/ directory). It will refuse to index home, root, or temp directories. To index a non-git directory, pass --force.
1. Install the binary
npm (macOS/Linux):
npm install -g @ontomics/ontomics
macOS (Homebrew):
brew install EtienneChollet/tap/ontomics
Shell installer (macOS/Linux):
curl --proto '=https' --tlsv1.2 -LsSf https://github.com/EtienneChollet/ontomics/releases/latest/download/ontomics-installer.sh | sh
From source:
git clone https://github.com/EtienneChollet/ontomics.git
cd ontomics
cargo build --release
2. Register with your harness
Claude Code:
claude mcp add -s user ontomics -- ontomics
Codex:
codex mcp add ontomics -- ontomics
OpenClaw:
openclaw mcp set ontomics '{"command":"ontomics"}'
pi-coding-agent:
pi install npm:@ontomics/ontomics
Share with your team — drop an .mcp.json in your repo root:
{
"mcpServers": {
"ontomics": {
"command": "npx",
"args": ["-y", "@ontomics/ontomics", "--repo", "."]
}
}
}
Supported languages
Python, TypeScript, JavaScript, Rust. Auto-detected from file extensions.
Tools
Concepts and vocabulary
| Tool | What it does |
|---|---|
query_concept | Find all variants, related concepts, and occurrences of a term |
locate_concept | Find the key signatures, classes, and files for a concept |
describe_symbol | Get the signature, docstring, and relationships for a function or class |
trace_concept | Trace how a concept flows through the codebase via call chains |
list_concepts | List the top domain concepts by frequency |
list_conventions | List all detected naming patterns (prefixes, suffixes, conversions) |
list_entities | List code entities (classes, functions) filtered by concept, role, or kind |
check_naming | Check an identifier against project conventions; suggests the canonical form |
suggest_name | Generate an identifier name that fits the project's vocabulary |
vocabulary_health | Measure convention coverage, naming consistency, and cluster cohesion |
ontology_diff | Show new, changed, or removed domain concepts since a git ref |
export_domain_pack | Export domain knowledge as portable YAML for use in other repos |
Behavioral similarity
| Tool | What it does |
|---|---|
find_similar_logic | Find functions with behaviorally similar implementations, ranked by embedding similarity |
describe_logic | Get the behavioral description, body text, and logic cluster membership for a function |
compact_context | Assemble tiered context (concepts + logic) for a symbol, optimized for LLM consumption |
Codebase structure
| Tool | What it does |
|---|---|
describe_file | Overview of a file's entities, concepts, and relationships |
concept_map | Show which modules contain which domain concepts |
type_flows | Show dominant types and how data flows through the codebase |
trace_type | Trace how a specific type propagates across files and call sites |
Resources
| Resource | What it does |
|---|---|
ontomics://briefing | Session briefing: top conventions, abbreviations, key concepts, contrastive pairs, and vocabulary warnings. Also available via ontomics briefing CLI. |
How it works
ontomics runs a multi-stage pipeline entirely on your machine — no API keys required:
- Parse — tree-sitter extracts every identifier, signature, and call site from your source files
- Analyze — TF-IDF scoring identifies domain-specific concepts and detects naming conventions
- Embed (concepts) — BGE-small (384-dim) clusters related concepts by semantic similarity
- Embed (logic) — CodeRankEmbed (768-dim) embeds raw function bodies and clusters them by behavioral similarity
- Centrality — PageRank scores entities by structural importance
Both embedding models are downloaded once on first run and cached locally. The index lives at <repo>/.ontomics/index.db — subsequent startups load from cache and watch for file changes.
Configuration via .ontomics/config.toml in the repo root. All fields have sensible defaults. See SPEC.md for the full design contract.
Featured
Keep your Mac awake while Claude Code and 40+ AI agents run. Sleeps when they're idle.
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Package@ontomics/ontomics
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UpdatedApr 14, 2026
