# Rarefaction (npm · rarefaction-lsp-mcp)

LSP call graph for coding agents: a symbol's callers, callees, tests and live files in one call.

- Trust score: 89/100 (high trust)
- Change this week: +3
- Registry status: active
- Liveness: live
- Owner verified: no
- Last scored: 2026-11-05

## Components

- npm · `rarefaction-lsp-mcp`: 89/100 (this document), [markdown](https://verifymcp.io/servers/ip2k-rarefaction-lsp-mcp/rarefaction-lsp-mcp.md), [page](https://verifymcp.io/servers/ip2k-rarefaction-lsp-mcp/rarefaction-lsp-mcp)

## Channel facts

- Registry: `npm`
- Package: `rarefaction-lsp-mcp`
- Version: `0.4.2`
- Transport: `stdio`

## Trust breakdown

How this component scores in each security and reliability category. Every signal is checked automatically from public evidence about the published package, including repeated runs of it in an isolated sandbox, and we only credit what we can confirm. Scores are 0–100 per category. Scoring method: https://verifymcp.io/docs/scoring (what has changed: https://verifymcp.io/docs/scoring/changelog)

Scored 2026-11-05.

- **Supply Chain Security**: 100/100
  - No malware found by supply-chain analysis.
  - No known CVEs affecting this package version or its production dependencies.
  - No install/post-install scripts declared.
  - 1 of 11 dependencies flagged as unhealthy.
- **Provenance & Transparency**: 97/100
  - Source repository is publicly reachable at the declared URL.
  - Cryptographically verified build provenance (signed, bound to ip2k/rarefaction).
  - Clear OSI-approved license (GPL-3.0-or-later).
  - Actively maintained (last published 15 days ago).
  - Disclosure check failed: no security disclosure policy was found in the source repository.
- **Schema Quality & AI Usability**: 66/100
  - AI-judged instruction clarity (excellent).
  - Context-footprint check failed: tool/resource definitions use about 730 tokens (~243/item across 3 items; 3 tools + 0 resources), over budget; trim descriptions and params.
  - Usage-examples check failed: none of the tools include examples.
- **Stability & Change Management**: 70/100
  - Stability observed for 21 of 30 days with no destabilising changes; credit accrues until the full window elapses.
- **Tool Coverage**: 100/100
  - 100% of tools have a non-trivial description (not blank, and not just the tool's name).
  - 100% of tool parameters carry a description.
  - Structured output schemas are declared (100% of tools); any adoption earns full credit.
- **Tool Safety**: 100/100
  - No prompt-injection markers were found in the server instructions, tool names or descriptions we captured.
  - We read all 3 captured tool definition(s), and no name or description among them implies an irreversible operation.
  - An AI judge read all 3 captured unit(s) of tool text and found none that tries to manipulate the model reading it.
- **Capabilities**: 100/100
  - Implements a supported MCP spec version (2025-11-25); the latest is 2026-07-28.

## Install

### How do I install the Rarefaction MCP server?

Rarefaction runs locally as an npm package, launched with npx -y rarefaction-lsp-mcp. Ready-made configuration for Claude, Cursor, VS Code, Codex and 5 more is on this page, copied from each client's own documentation.

### Claude

```bash
claude mcp add ip2k-rarefaction-lsp-mcp -- npx -y rarefaction-lsp-mcp
```

### Cursor

```json
{
  "mcpServers": {
    "ip2k-rarefaction-lsp-mcp": {
      "command": "npx",
      "args": [
        "-y",
        "rarefaction-lsp-mcp"
      ]
    }
  }
}
```

### VS Code

```json
{
  "servers": {
    "ip2k-rarefaction-lsp-mcp": {
      "command": "npx",
      "args": [
        "-y",
        "rarefaction-lsp-mcp"
      ]
    }
  }
}
```

### Codex

```bash
codex mcp add ip2k-rarefaction-lsp-mcp -- npx -y rarefaction-lsp-mcp
```

### opencode

```json
{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "ip2k-rarefaction-lsp-mcp": {
      "type": "local",
      "command": [
        "npx",
        "-y",
        "rarefaction-lsp-mcp"
      ],
      "enabled": true
    }
  }
}
```

### OpenClaw

```bash
openclaw mcp add ip2k-rarefaction-lsp-mcp --command npx --arg -y --arg rarefaction-lsp-mcp
```

### Hermes

```yaml
mcp_servers:
  ip2k-rarefaction-lsp-mcp:
    command: "npx"
    args: ["-y", "rarefaction-lsp-mcp"]
```

### Netclaw

```json
{
  "McpServers": {
    "ip2k-rarefaction-lsp-mcp": {
      "Transport": "stdio",
      "Command": "npx",
      "Arguments": [
        "-y",
        "rarefaction-lsp-mcp"
      ]
    }
  }
}
```

### Vellum

```bash
assistant mcp add ip2k-rarefaction-lsp-mcp -t stdio -c npx -a -y rarefaction-lsp-mcp
```

### Other

```json
{
  "mcpServers": {
    "ip2k-rarefaction-lsp-mcp": {
      "command": "npx",
      "args": [
        "-y",
        "rarefaction-lsp-mcp"
      ]
    }
  }
}
```

## Changelog

Every change recorded for this component, newest first. Days that predate change tracking, or that we cannot explain, say so: "we were watching and nothing happened" and "we were not watching" are different claims.

### 2026-11-04 (score 89, +1)

No change was recorded against any check on this day. Stability & Change Management went from 63 to 67. That category is still filling its 30-day observation window: 19 days of observed history at the previous scan, 20 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-11-03 (score 88, 0)

- [functional] Package version: 0.2.1 → 0.4.2

### 2026-11-02 (score 88, +1)

No change was recorded against any check on this day. Stability & Change Management went from 57 to 60. That category is still filling its 30-day observation window: 17 days of observed history at the previous scan, 18 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-31 (score 87, +1)

- [functional] Package version: 0.2.1 → 0.4.2

### 2026-10-29 (score 86, +1)

No change was recorded against any check on this day. Stability & Change Management went from 43 to 47. That category is still filling its 30-day observation window: 13 days of observed history at the previous scan, 14 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-27 (score 85, +1)

No change was recorded against any check on this day. Stability & Change Management went from 37 to 40. That category is still filling its 30-day observation window: 11 days of observed history at the previous scan, 12 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-25 (score 84, +1)

No change was recorded against any check on this day. Stability & Change Management went from 30 to 33. That category is still filling its 30-day observation window: 9 days of observed history at the previous scan, 10 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-22 (score 83, +16)

- [security improvement] Malware scan: unverified → pass

## MCP tools (3)

### `orient` (~319 tokens)

Orient on a symbol

Compact source context from language-server indexes: signature, body, callers, callees, tests, implementations and relevant files. Use before broad file reads in Swift, Rust, C/C++, TypeScript/JavaScript, Python and WebAssembly WAT projects. In mixed workspaces specify profile or use path:line:column. No cross-language/FFI edges are inferred. Increase up/down only when needed.

Input parameters:

- `down` (integer): How many levels of callees to walk (default 1).
- `include_body` (boolean): Include the symbol's source body.
- `max_body_lines` (integer): Truncate the body after this many lines.
- `max_nodes` (integer): Maximum graph nodes per direction and reference contexts; lower it for compact answers.
- `profile` (string): Source-language profile; required for bare names in mixed workspaces.
- `project` (string): Workspace-relative project directory, e.g. tools/driver for a nested Cargo package. Without it, a path:line:column symbol is answered from its enclosing Cargo workspace, else from its nearest project…
- `symbol` (string, required): A function, method, type or property: "updateLocation", "Engine.updateLocation", or an exact position "Sources/Engine.swift:204:10" (1-based line:column, on the name).
- `up` (integer): How many levels of callers to walk (default 2: test cases usually sit one helper above the code they exercise).

Output parameters:

- `body` (object)
- `callees` (array)
- `callers` (array)
- `external_callees_omitted` (integer): SDK / package callees dropped from `callees`.
- `freshness` (object)
- `implementations` (array)
- `live_files` (array): Files that can affect or be affected by the symbol within the walked depth.
- `profile` (string)
- `project_source_files` (integer)
- `reference_contexts` (array)
- `references` (array): For non-callables or servers without hierarchy: references grouped by file.
- `root` (string)
- `stats` (object)
- `symbol` (object)
- `test_run_hint` (object)
- `tests` (array)
- `truncated` (boolean)
- `type_hierarchy` (object)
- `warnings` (array)

### `scope` (~285 tokens)

Working set for a change

The files a change to one symbol is likely to touch: orient's call-graph files (callers, callees, implementations, tests) plus files that have historically changed in the same commits as the symbol's file, each with its reason. Use when planning an edit, to know which files to read and check. Advisory, not a boundary: real changes often touch files outside it.

Input parameters:

- `down` (integer): How many levels of callees to walk (default 1).
- `max_nodes` (integer): Maximum graph nodes per direction and reference contexts; lower it for compact answers.
- `profile` (string): Source-language profile; required for bare names in mixed workspaces.
- `project` (string): Workspace-relative project directory, e.g. tools/driver for a nested Cargo package. Without it, a path:line:column symbol is answered from its enclosing Cargo workspace, else from its nearest project…
- `symbol` (string, required): A function, method, type or property: "updateLocation", "Engine.updateLocation", or an exact position "Sources/Engine.swift:204:10" (1-based line:column, on the name).
- `up` (integer): How many levels of callers to walk (default 2: test cases usually sit one helper above the code they exercise).

Output parameters:

- `co_change` (object)
- `counts` (object)
- `files` (array): The working set: symbol file first, then call-graph files, then files found only through history or links.
- `profile` (string)
- `root` (string)
- `stats` (object)
- `symbol` (object)
- `truncated` (boolean): The call-graph walk hit max_nodes.
- `warnings` (array)

### `status` (~126 tokens)

Project, language server and index status

Check detected source-language profiles, project roots, executables, compile flags and freshness. Call once before orient in a new project or when orientation is incomplete. Pass profile/project to inspect a nested package.

Input parameters:

- `profile` (string): Source-language profile; required for bare names in mixed workspaces.
- `project` (string): Workspace-relative project directory, e.g. tools/driver for a nested Cargo package. Without it, a path:line:column symbol is answered from its enclosing Cargo workspace, else from its nearest project…

Output parameters:

- `profiles` (array)
- `root` (string)

## Diagnostics

Captured diagnostic sections: Provenance, Dependencies. The full working is on the page: https://verifymcp.io/servers/ip2k-rarefaction-lsp-mcp/rarefaction-lsp-mcp#diagnostics

## Score history

- 2026-11-05: 89
- 2026-11-04: 89
- 2026-11-03: 88
- 2026-11-02: 88
- 2026-11-01: 87
- 2026-10-31: 87
- 2026-10-30: 86
- 2026-10-29: 86
- 2026-10-28: 85
- 2026-10-27: 85
- 2026-10-26: 84
- 2026-10-25: 84
- 2026-10-24: 83
- 2026-10-23: 83
- 2026-10-22: 83
- 2026-10-21: 67
- 2026-10-20: 82
- 2026-10-19: 81
- 2026-10-18: 81
- 2026-10-17: 81
- 2026-10-16: 80
- 2026-10-15: 65
- 2026-10-14: 49

## Common questions

### What is the Rarefaction MCP server?

Rarefaction is an MCP server listed in the public MCP registry as io.github.ip2k/rarefaction-lsp-mcp. LSP call graph for coding agents: a symbol's callers, callees, tests and live files in one call. This page covers its npm package (rarefaction-lsp-mcp).

### Is the Rarefaction MCP server safe to use?

Rarefaction scores 89 out of 100 on VerifyMCP. We found no known CVEs affecting it as of 5 November 2026. It declares no install or post-install scripts. Its build provenance is signed and verified. That is a record of what we were able to check automatically, not an endorsement. The category breakdown on this page shows every signal behind the number, including the ones we could not confirm.

### What tools does the Rarefaction MCP server expose?

Rarefaction exposes 3 tools: orient, scope, status. Their descriptions and schemas cost roughly 730 tokens of context every time the server is loaded.

### Is the Rarefaction MCP server still maintained?

Rarefaction is still listed as active in the MCP registry. We last reached this channel on 5 November 2026. Those dates come from our own scans of the registry and the channel itself, not from anything the publisher announced.

### What licence is the Rarefaction MCP server under?

Rarefaction declares the GPL-3.0-or-later licence, which is OSI-approved. That covers the source only, and says nothing about the cost of any service it calls.

## Links

- npm package: https://www.npmjs.com/package/rarefaction-lsp-mcp
- Socket report: https://socket.dev/npm/package/rarefaction-lsp-mcp
- Repository: https://github.com/ip2k/rarefaction
- Changelog RSS feed: https://verifymcp.io/servers/ip2k-rarefaction-lsp-mcp/rarefaction-lsp-mcp.xml
- Changelog JSON feed: https://verifymcp.io/servers/ip2k-rarefaction-lsp-mcp/rarefaction-lsp-mcp.json
- HTML version of this page: https://verifymcp.io/servers/ip2k-rarefaction-lsp-mcp/rarefaction-lsp-mcp