# Jarroba Tools · Calculation (npm · @jarroba/mcp-calc)

Maths a model gets wrong: units with dimensional checking, equations, sheets. 5 tools, local.

- Trust score: 66/100 (medium)
- Change this week: +4
- Registry status: active
- Liveness: live
- Owner verified: no
- Last scored: 2026-09-26

## Components

- npm · `@jarroba/mcp-calc`: 66/100 (this document), [markdown](https://verifymcp.io/servers/invarato-jarroba-tools-calc/jarroba-mcp-calc.md), [page](https://verifymcp.io/servers/invarato-jarroba-tools-calc/jarroba-mcp-calc)

## Channel facts

- Registry: `npm`
- Package: `@jarroba/mcp-calc`
- Version: `0.1.4`
- 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 2026-09-26.

- **Supply Chain Security**: 98/100
  - No malware found by supply-chain analysis.
  - No known CVEs affecting this package version or its production dependencies.
  - No install/post-install scripts declared.
  - 35 of 106 dependencies flagged as unhealthy.
- **Provenance & Transparency**: 19/100
  - Repository check failed: the declared repository URL returned HTTP 404.
  - Provenance check failed: no build-provenance attestation is published.
  - Clear OSI-approved license (MIT).
  - Actively maintained (last published 9 days ago).
  - Security-disclosure policy not yet verified: we couldn't inspect the source repository.
- **Schema Quality & AI Usability**: 67/100
  - AI-judged instruction clarity (good).
  - Context-footprint check failed: tool/resource definitions use about 808 tokens (~161/item across 5 items; 5 tools + 0 resources), over budget; trim descriptions and params.
  - Usage-examples check failed: none of the tools include examples.
- **Stability & Change Management**: 33/100
  - Stability observed for 10 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.
- **Tool Safety**: 75/100
  - No prompt-injection markers were found in the server instructions, tool names or descriptions we captured.
  - 0 of 1 tool(s) whose name or description implies an irreversible operation declare an MCP destructiveHint annotation; "calc_eval" implies "eval" and declares readOnlyHint instead, contradicting what its own name says it does.
  - An AI judge read all 6 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 Jarroba Tools · Calculation MCP server?

Jarroba Tools · Calculation runs locally as an npm package, launched with npx -y @jarroba/mcp-calc. 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 invarato-jarroba-tools-calc -- npx -y @jarroba/mcp-calc
```

### Cursor

```json
{
  "mcpServers": {
    "invarato-jarroba-tools-calc": {
      "command": "npx",
      "args": [
        "-y",
        "@jarroba/mcp-calc"
      ]
    }
  }
}
```

### VS Code

```json
{
  "servers": {
    "invarato-jarroba-tools-calc": {
      "command": "npx",
      "args": [
        "-y",
        "@jarroba/mcp-calc"
      ]
    }
  }
}
```

### Codex

```bash
codex mcp add invarato-jarroba-tools-calc -- npx -y @jarroba/mcp-calc
```

### opencode

```json
{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "invarato-jarroba-tools-calc": {
      "type": "local",
      "command": [
        "npx",
        "-y",
        "@jarroba/mcp-calc"
      ],
      "enabled": true
    }
  }
}
```

### OpenClaw

```bash
openclaw mcp add invarato-jarroba-tools-calc --command npx --arg -y --arg @jarroba/mcp-calc
```

### Hermes

```yaml
mcp_servers:
  invarato-jarroba-tools-calc:
    command: "npx"
    args: ["-y", "@jarroba/mcp-calc"]
```

### Netclaw

```json
{
  "McpServers": {
    "invarato-jarroba-tools-calc": {
      "Transport": "stdio",
      "Command": "npx",
      "Arguments": [
        "-y",
        "@jarroba/mcp-calc"
      ]
    }
  }
}
```

### Vellum

```bash
assistant mcp add invarato-jarroba-tools-calc -t stdio -c npx -a -y @jarroba/mcp-calc
```

### Other

```json
{
  "mcpServers": {
    "invarato-jarroba-tools-calc": {
      "command": "npx",
      "args": [
        "-y",
        "@jarroba/mcp-calc"
      ]
    }
  }
}
```

## 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.

### 2026-09-25 (score 66, 0)

- [functional] We updated how we score, so this day's move reflects our rubric, not a change to the server

### 2026-09-24 (score 66, +4)

- [functional improvement] Stability: unverified → 0.27

### 2026-09-16 (score 62)

First indexed and scored.

## MCP tools (5)

### `calc_eval` (~108 tokens)

Evaluate a mathematical expression WITH UNITS and dimensional checking: "100 km/h to m/s", "5 km + 300 m", "70 kg to lbs", "det([[1,2],[3,4]])". Adding incompatible units is an error, not a silent number. Also flags results that are not finite (NaN, infinity).

Input parameters:

- `expression` (string, required): e.g. "100 km/h to m/s" or "sqrt(2)^2 + 2^10"

### `calc_solve` (~139 tokens)

Solve an equation in one unknown ("x^2 - 5x + 6 = 0", "sin(x) = 0.5") or a linear system (one equation per line). Says whether the answer is EXACT or an approximation, and over which interval it searched. Never invents a root it did not find.

Input parameters:

- `equations` (string, required): One equation, or several separated by newlines for a system
- `from` (number): Lower bound for the numeric search
- `to` (number): Upper bound for the numeric search
- `unknown` (string): Which variable to solve for (guessed if omitted)

### `calc_sheet` (~141 tokens)

Evaluate a multi-line calculation sheet and return the result of EVERY line. Variables carry downwards, units travel with the value, "#" starts a comment, "ans" is the previous result, and an error stays on its own line instead of killing the sheet. Declare currencies with "# @moneda USD = 1.08 EUR". Good for checking a quote or a budget line by line.

Input parameters:

- `as_markdown` (boolean): Also return the sheet as a Markdown table
- `sheet` (string, required): One expression per line, e.g. "width = 3.5 m height = 2.4 m area = width * height"

### `calc_derive` (~192 tokens)

Differentiate an expression symbolically, exactly: "x^3 + 2x", "sin(x)*cos(x)", "x^x". Keeps units, so d/dx (3 m * x) is "3 m" and not 3. Can take higher-order derivatives and evaluate the result at a point. Says which name it read as a unit, and refuses to answer "0" when the variable is not in the expression.

Input parameters:

- `at` (number): Also evaluate the derivative at this value of the variable
- `expression` (string, required): e.g. "x^3 + 2x" or "9.8 m/s^2 * t^2 / 2"
- `order` (integer): 1 = first derivative, 2 = second… up to 4
- `variable` (string): Differentiate with respect to this (guessed if omitted)

### `calc_steps` (~165 tokens)

Show the WORKED STEPS of a calculation, verified step by step: a linear or quadratic equation, a derivative (naming which rule applies), or Gaussian elimination on a linear system row by row. Each step comes with the name of the rule used. When it cannot explain a case it says so (covered: false) instead of inventing a plausible-looking derivation — useful when you have to show your work to a person.

Input parameters:

- `input` (string, required): An equation ("2x + 6 = 0"), an expression to differentiate ("sin(x)*x^2"), or one equation per line for a system
- `kind` (string): What to explain
- `variable` (string): The unknown or the variable to differentiate by (guessed if omitted)

## Diagnostics

Captured diagnostic sections: Provenance, Dependencies. The full working is on the page: https://verifymcp.io/servers/invarato-jarroba-tools-calc/jarroba-mcp-calc#diagnostics

## Score history

- 2026-09-26: 66
- 2026-09-25: 66
- 2026-09-24: 66
- 2026-09-23: 62
- 2026-09-22: 62
- 2026-09-21: 62
- 2026-09-20: 62
- 2026-09-19: 62
- 2026-09-18: 62
- 2026-09-17: 62
- 2026-09-16: 62

## Common questions

### What is the Jarroba Tools · Calculation MCP server?

Jarroba Tools · Calculation is an MCP server listed in the public MCP registry as io.github.Invarato/jarroba-tools-calc. Maths a model gets wrong: units with dimensional checking, equations, sheets. 5 tools, local. This page covers its npm package (@jarroba/mcp-calc).

### Is the Jarroba Tools · Calculation MCP server safe to use?

Jarroba Tools · Calculation scores 66 out of 100 on VerifyMCP. We found no known CVEs affecting it as of 26 September 2026. It declares no install or post-install scripts. 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 Jarroba Tools · Calculation MCP server expose?

Jarroba Tools · Calculation exposes 5 tools: calc_eval, calc_solve, calc_sheet, calc_derive, calc_steps. Their descriptions and schemas cost roughly 745 tokens of context every time the server is loaded.

### Is the Jarroba Tools · Calculation MCP server still maintained?

Jarroba Tools · Calculation is still listed as active in the MCP registry. We last reached this channel on 26 September 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 Jarroba Tools · Calculation MCP server under?

Jarroba Tools · Calculation declares the MIT 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/@jarroba/mcp-calc
- Socket report: https://socket.dev/npm/package/@jarroba/mcp-calc
- Changelog RSS feed: https://verifymcp.io/servers/invarato-jarroba-tools-calc/jarroba-mcp-calc.xml
- Changelog JSON feed: https://verifymcp.io/servers/invarato-jarroba-tools-calc/jarroba-mcp-calc.json
- HTML version of this page: https://verifymcp.io/servers/invarato-jarroba-tools-calc/jarroba-mcp-calc