# io.github.WSattazahn/caveat-lang (npm · caveat-lang)

Authoring bridge for Caveat: validate, check and test programs; explain decisions; find dependents.

- Trust score: 93/100 (high trust)
- Change this week: +3
- Registry status: active
- Liveness: live
- Owner verified: no
- Last scored: 2026-11-05

## Components

- npm · `caveat-lang`: 93/100 (this document), [markdown](https://verifymcp.io/servers/wsattazahn-caveat-lang/caveat-lang.md), [page](https://verifymcp.io/servers/wsattazahn-caveat-lang/caveat-lang)

## Channel facts

- Registry: `npm`
- Package: `caveat-lang`
- Version: `1.4.1`
- 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 2026-11-05.

- **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.
  - No production dependencies, so there is no dependency health to assess.
- **Provenance & Transparency**: 100/100
  - Source repository is publicly reachable at the declared URL.
  - Cryptographically verified build provenance (signed, bound to WSattazahn/caveat-lang).
  - Clear OSI-approved license (MIT).
  - Actively maintained (last published 9 days ago).
  - Publishes a security disclosure policy (SECURITY.md).
- **Schema Quality & AI Usability**: 60/100
  - AI-judged instruction clarity (excellent).
  - Context-footprint check failed: tool/resource definitions use about 1876 tokens (~375/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**: 100/100
  - No destabilizing schema changes in the last 30 days.
- **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 5 captured tool definition(s), and no name or description among them implies an irreversible operation.
  - 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 current MCP spec version (2026-07-28).

## Install

### How do I install the io.github.WSattazahn/caveat-lang MCP server?

io.github.WSattazahn/caveat-lang runs locally as an npm package, launched with npx -y caveat-lang 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 wsattazahn-caveat-lang -- npx -y caveat-lang mcp
```

### Cursor

```json
{
  "mcpServers": {
    "wsattazahn-caveat-lang": {
      "command": "npx",
      "args": [
        "-y",
        "caveat-lang",
        "mcp"
      ]
    }
  }
}
```

### VS Code

```json
{
  "servers": {
    "wsattazahn-caveat-lang": {
      "command": "npx",
      "args": [
        "-y",
        "caveat-lang",
        "mcp"
      ]
    }
  }
}
```

### Codex

```bash
codex mcp add wsattazahn-caveat-lang -- npx -y caveat-lang mcp
```

### opencode

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

### OpenClaw

```bash
openclaw mcp add wsattazahn-caveat-lang --command npx --arg -y --arg caveat-lang --arg mcp
```

### Hermes

```yaml
mcp_servers:
  wsattazahn-caveat-lang:
    command: "npx"
    args: ["-y", "caveat-lang", "mcp"]
```

### Netclaw

```json
{
  "McpServers": {
    "wsattazahn-caveat-lang": {
      "Transport": "stdio",
      "Command": "npx",
      "Arguments": [
        "-y",
        "caveat-lang",
        "mcp"
      ]
    }
  }
}
```

### Vellum

```bash
assistant mcp add wsattazahn-caveat-lang -t stdio -c npx -a -y caveat-lang mcp
```

### Other

```json
{
  "mcpServers": {
    "wsattazahn-caveat-lang": {
      "command": "npx",
      "args": [
        "-y",
        "caveat-lang",
        "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 93, +1)

- [security] Stability: 0.97 → pass

### 2026-11-02 (score 92, +1)

No change was recorded against any check on this day. Stability & Change Management went from 90 to 93. That category is still filling its 30-day observation window: 27 days of observed history at the previous scan, 28 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-31 (score 91, +1)

No change was recorded against any check on this day. Stability & Change Management went from 83 to 87. That category is still filling its 30-day observation window: 25 days of observed history at the previous scan, 26 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-28 (score 90, +27)

- [security improvement] Malware scan: unverified → pass
- [security improvement] Known CVEs: unverified → pass
- [functional improvement] Dependency health: unverified → pass
- [functional] Package version: 0.1.0-rc.19 → 1.4.1

### 2026-10-27 (score 63, −11)

- [security regression] Known CVEs: pass → unverified
- [functional regression] Dependency health: pass → unverified
- [functional] Package version: 1.4.0 → 1.4.1

### 2026-10-26 (score 74, −14)

- [security regression] Malware scan: pass → unverified
- [functional improvement] Security disclosure: fail → pass
- [functional] Package version: 1.3.0 → 1.4.0

### 2026-10-25 (score 88, +16)

- [security improvement] Malware scan: unverified → pass

### 2026-10-24 (score 72, −15)

- [security regression] Malware scan: pass → unverified
- [functional] Package version: 1.2.0 → 1.3.0

## MCP tools (5)

### `caveat_validate` (~218 tokens)

Load inline source with the installed runtime and list its declarations. Start here to find load errors; use caveat_check for authoring diagnostics and caveat_test to verify expected behavior. No events are dispatched. report (caveat-validate/0.1) contains program, loads, events, reading_streams, decision_series and displayed bindings, or a load error. exitCode: 0 loaded; 2 load failure. Returns the same JSON in structuredContent and text: {schema:"caveat-authoring/0.1",operation,sourceSha256,runtime,exitCode,report}. Read exitCode even when isError is false. Bridge failures instead set isError:true with {schema:"caveat-authoring-error/0.1",error:{kind,message}}.

Input parameters:

- `source` (string, required): Complete inline Caveat program text, available as the virtual file inline.cav. No file path or URL lookup. At most 1 MiB of UTF-8 source; each call uses a fresh runtime.

### `caveat_check` (~300 tokens)

Load a single-file program and report authoring diagnostics, such as repeated rules or a missing reopening path. Use after editing source; choose caveat_validate for a declaration summary and caveat_test for behavior assertions. A clean check does not prove behavior; bundles are unsupported. report (caveat-check/0.1) contains loads, strict, diagnostics and suppressed diagnostics, with code, location, message and suggestion, or a load error. exitCode: 0 completed without a strict failure; 1 strict with unsuppressed diagnostics; 2 load failure or bundle. Returns the same JSON in structuredContent and text: {schema:"caveat-authoring/0.1",operation,sourceSha256,runtime,exitCode,report}. Read exitCode even when isError is false. Bridge failures instead set isError:true with {schema:"caveat-authoring-error/0.1",error:{kind,message}}.

Input parameters:

- `source` (string, required): Complete inline Caveat program text, available as the virtual file inline.cav. No file path or URL lookup. At most 1 MiB of UTF-8 source; each call uses a fresh runtime.
- `strict` (boolean): Optional, defaults to false. When true, any unsuppressed diagnostic makes exitCode 1 instead of 0; suppressed diagnostics do not count. Does not change program behavior. Load failures and unsupported…

### `caveat_test` (~511 tokens)

Run scenario assertions and runtime invariant checks against inline source, with a fresh session per scenario. Use to verify expected event outcomes and snapshot values; caveat_validate only checks loading, caveat_check reports diagnostics, and caveat_explain inspects history without assertions. report (caveat-scenario-report/0.1) includes files, per-scenario results/failures, check diagnostics and passed/failed totals. exitCode: 0 all passed; 1 scenario failure; 2 invalid scenario document (report has valid:false and error) or blocking authoring diagnostics. Every source reference must be inline.cav. Returns the same JSON in structuredContent and text: {schema:"caveat-authoring/0.1",operation,sourceSha256,runtime,exitCode,report}. Read exitCode even when isError is false. Bridge failures instead set isError:true with {schema:"caveat-authoring-error/0.1",error:{kind,message}}.

Input parameters:

- `scenarios` (object, required): Scenario document object, not JSON text. Example: {"schema":"caveat-scenarios/0.1","source":"inline.cav","scenarios":[{"id":"initial","title":"Initial sequence","steps":[{"expect":{"/sequence":0}}]}]…
- `source` (string, required): Complete inline Caveat program text, available as the virtual file inline.cav. No file path or URL lookup. At most 1 MiB of UTF-8 source; each call uses a fresh runtime.

### `caveat_explain` (~320 tokens)

Replay optional events and explain the resulting decisions, evidence and displayed values. Use to answer why a decision was made; choose caveat_dependents to trace one evidence or caveat name forward, and caveat_test for assertions. report (caveat-explain/0.1) includes sequence, event outcomes, decisions with grounds and revision history, evidence with caveats, displayed values and available archive history. exitCode: 0 replay completed (may include rejected events); 1 fatal event with last good state; 2 source load failure (report has loads:false and error). Returns the same JSON in structuredContent and text: {schema:"caveat-authoring/0.1",operation,sourceSha256,runtime,exitCode,report}. Read exitCode even when isError is false. Bridge failures instead set isError:true with {schema:"caveat-authoring-error/0.1",error:{kind,message}}.

Input parameters:

- `events` (array): Events replayed in array order from a fresh session. Omitted or [] inspects the initial state; previous calls supply no history. Rejections are recorded and replay continues; a fatal event stops repl…
- `source` (string, required): Complete inline Caveat program text, available as the virtual file inline.cav. No file path or URL lookup. At most 1 MiB of UTF-8 source; each call uses a fresh runtime.

### `caveat_dependents` (~502 tokens)

Replay optional events and find what rests on one named evidence item, reading stream or caveat. Use for impact inspection; caveat_explain instead explains all decisions and their reasons. Subjects are causes only: evidence, a reading stream or a caveat. Claims and decisions are never subjects, because a claim causes nothing and the grounds of a decision are evidence, not claims; both appear in the report as what the subject reaches. To trace from a claim, query the evidence that supports or opposes it (report.claims lists those relations). report (caveat-dependents/0.1) includes subject, kind, sequence, event outcomes, claims, decisions, changes, values, displayed values and withdrawal records; dependency entries distinguish grounds from possible influence through lineage. exitCode: 0 replay completed (may include rejected events); 1 fatal event with last good state; 2 load failure or unknown subject, with report.error. Returns the same JSON in structuredContent and text: {schema:"caveat-authoring/0.1",operation,sourceSha256,runtime,exitCode,report}. Read exitCode even when isError is false. Bridge failures instead set isError:true with {schema:"caveat-authoring-error/0.1",error:{kind,message}}.

Input parameters:

- `events` (array): Events replayed in array order from a fresh session. Omitted or [] inspects the initial state; previous calls supply no history. Rejections are recorded and replay continues; a fatal event stops repl…
- `source` (string, required): Complete inline Caveat program text, available as the virtual file inline.cav. No file path or URL lookup. At most 1 MiB of UTF-8 source; each call uses a fresh runtime.
- `subject` (string, required): Exact case-sensitive evidence name, reading stream name, caveat name, or evidence occurrence ID after replay. Evidence records supplied observations; a reading stream is a named history of samples; a…

## Diagnostics

Captured diagnostic sections: Provenance, Dependencies. The full working is on the page: https://verifymcp.io/servers/wsattazahn-caveat-lang/caveat-lang#diagnostics

## Score history

- 2026-11-05: 93
- 2026-11-04: 93
- 2026-11-03: 92
- 2026-11-02: 92
- 2026-11-01: 91
- 2026-10-31: 91
- 2026-10-30: 90
- 2026-10-29: 90
- 2026-10-28: 90
- 2026-10-27: 63
- 2026-10-26: 74
- 2026-10-25: 88
- 2026-10-24: 72
- 2026-10-23: 87
- 2026-10-22: 86
- 2026-10-21: 86
- 2026-10-20: 70
- 2026-10-19: 70
- 2026-10-18: 84
- 2026-10-17: 69
- 2026-10-16: 83
- 2026-10-15: 68
- 2026-10-14: 49
- 2026-10-13: 49
- 2026-10-12: 49

## Common questions

### What is the io.github.WSattazahn/caveat-lang MCP server?

io.github.WSattazahn/caveat-lang is an MCP server listed in the public MCP registry as io.github.WSattazahn/caveat-lang. Authoring bridge for Caveat: validate, check and test programs; explain decisions; find dependents. This page covers its npm package (caveat-lang).

### Is the io.github.WSattazahn/caveat-lang MCP server safe to use?

io.github.WSattazahn/caveat-lang scores 93 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 io.github.WSattazahn/caveat-lang MCP server expose?

io.github.WSattazahn/caveat-lang exposes 5 tools: caveat_validate, caveat_check, caveat_test, caveat_explain, caveat_dependents. Their descriptions and schemas cost roughly 1,851 tokens of context every time the server is loaded.

### Is the io.github.WSattazahn/caveat-lang MCP server still maintained?

io.github.WSattazahn/caveat-lang 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 io.github.WSattazahn/caveat-lang MCP server under?

io.github.WSattazahn/caveat-lang declares the MIT licence, which is OSI-approved. That covers the source only, and says nothing about the cost of any service it calls.

### What did VerifyMCP test on the io.github.WSattazahn/caveat-lang MCP server?

VerifyMCP ran 16 checks on io.github.WSattazahn/caveat-lang, covering Malware scan, Known CVEs, Install scripts, Dependency health and 12 more. Endpoint Security and Transport & Reachability do not apply to an npm package, so they were not tested. The score does not measure everything, and the scoring documentation lists what it leaves out.

## Links

- npm package: https://www.npmjs.com/package/caveat-lang
- Socket report: https://socket.dev/npm/package/caveat-lang
- Repository: https://github.com/WSattazahn/caveat-lang
- Changelog RSS feed: https://verifymcp.io/servers/wsattazahn-caveat-lang/caveat-lang.xml
- Changelog JSON feed: https://verifymcp.io/servers/wsattazahn-caveat-lang/caveat-lang/changelog.json
- Trust report (JSON): https://verifymcp.io/servers/wsattazahn-caveat-lang/caveat-lang.json
- HTML version of this page: https://verifymcp.io/servers/wsattazahn-caveat-lang/caveat-lang