How do I install Ontomics?

Copy the stdio config for Cursor, Claude Desktop, Claude Code, or VS Code on this page. It uses the publisher's install, not a PlugMCP proxy.

Does Ontomics need an API key?

No required environment variable is listed on this record.

What transport does Ontomics use?

Ontomics runs locally over stdio.

When was Ontomics last checked?

Last checked 2026-11-09. Index your codebase's domain knowledge. 20x fewer tokens, 10x faster.

Ontomics MCP server

Power your agent

Add this server

The publisher's own command. Not a PlugMCP endpoint.

Add to Cursor Add to VS Code Run on PlugMCP

Host a copy with our keys and logs.

Local command

npx -y @ontomics/[email protected]

Claude Code has no install link for a local command. Copy the command below and run it in a terminal.

shClaude Code

1claude mcp add io.github.etiennechollet-ontomics -- npx -y @ontomics/ontomics@0.3.1

Run in a terminal.

jsonClaude Desktop

1{2  "mcpServers": {3    "io.github.etiennechollet-ontomics": {4      "command": "npx",5      "args": [6        "-y",7        "@ontomics/[email protected]"8      ]9    }10  }11}

claude_desktop_config.json

Local · npmPublisher installStep-by-step: add this in Claude

Remote URL or a command on your machine? How the two installs differ

Run on PlugMCP

Host a copy with our keys and logs.

A new server you create. It is not this listing's official endpoint. Use the publisher install when you want their URL and their credentials.

Launch

Server facts

Local

Transport: stdio
Version: 0.3.1
Last checked

Tools

No tool list yet. Remote servers get one after the first health check.

FAQ

Questions

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.

Add this server

Host a copy with our keys and logs.

Server facts

Tools

Questions

How do I install Ontomics?

Does Ontomics need an API key?

What transport does Ontomics use?

When was Ontomics last checked?

Documentation

ontomics

Benchmark

What it does that search can't

Behavioral similarity

Install

1. Install the binary

2. Register with your harness

Supported languages

Tools

Concepts and vocabulary

Behavioral similarity

Codebase structure

Resources

How it works