# TypeSafe Jev (npm · jevcore-mcp)

MCP server over TypeSafe Jev: typed ask, rank and check judgments return calibrated probabilities.

- Trust score: 65/100 (medium)
- Registry status: active
- Liveness: live
- Owner verified: no
- Last scored: 2026-09-26

## Components

- npm · `jevcore-mcp`: 65/100 (this document), [markdown](https://verifymcp.io/servers/perrylink-jevcore/jevcore-mcp.md), [page](https://verifymcp.io/servers/perrylink-jevcore/jevcore-mcp)

## Channel facts

- Registry: `npm`
- Package: `jevcore-mcp`
- Version: `0.4.1`
- 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.
  - 31 of 98 dependencies flagged as unhealthy.
- **Provenance & Transparency**: 23/100
  - Repository check failed: no source repository is declared.
  - Provenance check failed: no build-provenance attestation is published.
  - Clear OSI-approved license (Apache-2.0).
  - Actively maintained (last published 5 days ago).
  - Publishes a security disclosure policy (SECURITY.md).
- **Schema Quality & AI Usability**: 70/100
  - AI-judged instruction clarity (excellent).
  - Context-footprint check failed: tool/resource definitions use about 761 tokens (~253/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**: 0/100
  - Stability not yet verified: not enough scan history yet (needs a 30-day window).
- **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**: 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.

**Unverified: 1 category.** A category scored 0 because we could not verify it: a data source with nothing on this package, evidence we could not reach, or a check we could not run. We only credit what we can confirm.

## Install

### How do I install the TypeSafe Jev MCP server?

TypeSafe Jev runs locally as an npm package, launched with npx -y jevcore-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 perrylink-jevcore -- npx -y jevcore-mcp
```

### Cursor

```json
{
  "mcpServers": {
    "perrylink-jevcore": {
      "command": "npx",
      "args": [
        "-y",
        "jevcore-mcp"
      ]
    }
  }
}
```

### VS Code

```json
{
  "servers": {
    "perrylink-jevcore": {
      "command": "npx",
      "args": [
        "-y",
        "jevcore-mcp"
      ]
    }
  }
}
```

### Codex

```bash
codex mcp add perrylink-jevcore -- npx -y jevcore-mcp
```

### opencode

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

### OpenClaw

```bash
openclaw mcp add perrylink-jevcore --command npx --arg -y --arg jevcore-mcp
```

### Hermes

```yaml
mcp_servers:
  perrylink-jevcore:
    command: "npx"
    args: ["-y", "jevcore-mcp"]
```

### Netclaw

```json
{
  "McpServers": {
    "perrylink-jevcore": {
      "Transport": "stdio",
      "Command": "npx",
      "Arguments": [
        "-y",
        "jevcore-mcp"
      ]
    }
  }
}
```

### Vellum

```bash
assistant mcp add perrylink-jevcore -t stdio -c npx -a -y jevcore-mcp
```

### Other

```json
{
  "mcpServers": {
    "perrylink-jevcore": {
      "command": "npx",
      "args": [
        "-y",
        "jevcore-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.

### 2026-09-25 (score 65, 0)

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

### 2026-09-21 (score 65, +11)

- [security improvement] Known CVEs: unverified → pass
- [functional improvement] Dependency health: unverified → 0.86

### 2026-09-20 (score 54)

First indexed and scored.

## MCP tools (3)

### `jev_ask` (~285 tokens)

Ask Jev typed questions

Ask TypeSafe Jev one or more typed questions about a single piece of state. Jev does not generate text: it returns a selected option and calibrated probabilities. Use it for judgments the rest of the work branches on — routing, classifying, scoring, triaging. Do NOT use it to write prose, explain, summarize, or generate code.

Question types: "noul" is yes/no and returns the probability of true; "choice" picks one of the criteria keys you declare; "score" places the state on an ordered scale whose levels you declare in ascending order. A noul may also declare "boundary" — what true means and what false means — which is worth supplying whenever the line between them is not obvious.

Batch related questions into one call: they are answered against the same state in one round-trip. A score question answers with a numeric "score" that may fall between levels, a "legend" mapping each level index to its description, and probabilities per level. This tool returns probabilities, not decisions — apply your own confidence threshold before acting, and treat a low-confidence answer as unknown rather than picking for it.

Input parameters:

- `questions` (object, required): Map of question id to question. Ids are the keys of the response.
- `state`: The evidence to judge. This is transmitted to TypeSafe when a live key is configured.

### `jev_rank` (~344 tokens)

Rank candidates with Jev

Rank a list of candidates by how well each satisfies one stated criterion. Returns every candidate with an independent relevance probability, sorted. Use it to order search hits, triage a backlog, or find the one item that answers a question.

The probabilities are independent per-candidate judgments, NOT a distribution that sums to 1. A flat set of scores means "none of these stands out", not a fine-grained ordering.

What you send is capped, and the two caps behave differently. The candidate list is truncated at 16,000 characters, and the reply carries `truncated: true` when that happens — check for it, because a cut list is still ranked and the scores then describe what Jev actually read rather than what you sent. The generated questions are refused at 4,000 characters instead: exceeding that gives you an error asking for fewer or smaller items, never a silent best-N, so retrying the same call cannot help. Because the criterion is repeated into every candidate's question, that second cap is what bounds the candidate count — measured, an ordinary criterion fits 20 candidates and a 400-character criterion fits 7, while candidate length does not change the count at all and only starts truncating the list past roughly 1,600 characters per candidate.

Input parameters:

- `candidates` (array, required): One string per candidate. The serialized list is truncated at 16,000 characters, and the reply reports `truncated: true` when it was cut.
- `criterion` (string): What "relevant" means, as a yes/no question about one candidate.
- `query` (string, required): The task or question the candidates are ranked against.

### `jev_check` (~132 tokens)

Check a claim against evidence

Check whether a piece of evidence supports a specific claim. Returns "supported", "contradicted", "conflicted", "insufficient", or "unknown", with the underlying probabilities. The distinction between "not supported" and "contradicted" is the reason to use this rather than reading the evidence yourself.

It judges one claim against the evidence you give it. It does not search for evidence, and it cannot detect that you omitted the decisive passage.

Input parameters:

- `claim` (string, required): The single claim to check.
- `evidence` (string, required): The evidence to judge it against. Quote rather than paraphrase.

## Diagnostics

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

## Score history

- 2026-09-26: 65
- 2026-09-25: 65
- 2026-09-24: 65
- 2026-09-23: 65
- 2026-09-22: 65
- 2026-09-21: 65
- 2026-09-20: 54

## Common questions

### What is the TypeSafe Jev MCP server?

TypeSafe Jev is an MCP server listed in the public MCP registry as io.github.PerryLink/jevcore. MCP server over TypeSafe Jev: typed ask, rank and check judgments return calibrated probabilities. This page covers its npm package (jevcore-mcp).

### Is the TypeSafe Jev MCP server safe to use?

TypeSafe Jev scores 65 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 TypeSafe Jev MCP server expose?

TypeSafe Jev exposes 3 tools: jev_ask, jev_rank, jev_check. Their descriptions and schemas cost roughly 761 tokens of context every time the server is loaded.

### Is the TypeSafe Jev MCP server still maintained?

TypeSafe Jev 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 TypeSafe Jev MCP server under?

TypeSafe Jev declares the Apache-2.0 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/jevcore-mcp
- Socket report: https://socket.dev/npm/package/jevcore-mcp
- Changelog RSS feed: https://verifymcp.io/servers/perrylink-jevcore/jevcore-mcp.xml
- Changelog JSON feed: https://verifymcp.io/servers/perrylink-jevcore/jevcore-mcp.json
- HTML version of this page: https://verifymcp.io/servers/perrylink-jevcore/jevcore-mcp