# Syl Guardian (remote · guardian.sylai.io)

Causal check on AI agent claims, from ad-spend/ROAS lift to any decision: pass, caution or hold.

- Trust score: 65/100 (medium)
- Change this week: +3
- Registry status: active
- Liveness: live
- Owner verified: no
- Last scored: 2026-11-05

## Components

- remote · `guardian.sylai.io`: 65/100 (this document), [markdown](https://verifymcp.io/servers/io-sylai-guardian/guardian.md), [page](https://verifymcp.io/servers/io-sylai-guardian/guardian)

## Channel facts

- Endpoint: `https://guardian.sylai.io/mcp`
- Transports: `streamable-http`
- Auth: `none`
- Version: `0.3.1`

## Trust breakdown

How this component scores in each security and reliability category. Every signal is checked automatically against the live server, 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.

- **Endpoint Security**: 57/100
  - The endpoint's TLS certificate is valid, in date, and uses a strong key.
  - Authorisation not fully verified: no authorisation is required to call this server, and 2 tool(s) never declared a destructiveHint. The MCP spec treats an absent hint as destructive by default, so we cannot call this surface safe.
  - HTTPS is enforced; there's no plaintext access path.
  - HSTS check failed: the Strict-Transport-Security header is absent.
  - DNSSEC check failed: this domain isn't protected by DNSSEC.
- **Transport & Reachability**: 100/100
  - Verified streamable-http transport via a live MCP handshake.
- **Schema Quality & AI Usability**: 57/100
  - AI-judged instruction clarity (excellent).
  - Context-footprint check failed: tool/resource definitions use about 1573 tokens (~786/item across 2 items; 2 tools + 0 resources), over budget; trim descriptions and params.
  - Usage-examples check failed: none of the tools include examples.
- **Stability & Change Management**: 47/100
  - Stability observed for 14 of 30 days with no destabilising changes; credit accrues until the full window elapses.
- **Tool Coverage**: 67/100
  - 100% of tools have a non-trivial description (not blank, and not just the tool's name).
  - 0% 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 2 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 Syl Guardian MCP server?

Syl Guardian is a hosted endpoint at https://guardian.sylai.io/mcp, so there is nothing to install locally. 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 --transport http io-sylai-guardian 'https://guardian.sylai.io/mcp'
```

### Cursor

```json
{
  "mcpServers": {
    "io-sylai-guardian": {
      "url": "https://guardian.sylai.io/mcp"
    }
  }
}
```

### VS Code

```json
{
  "servers": {
    "io-sylai-guardian": {
      "type": "http",
      "url": "https://guardian.sylai.io/mcp"
    }
  }
}
```

### Codex

```toml
[mcp_servers.io-sylai-guardian]
url = "https://guardian.sylai.io/mcp"
```

### opencode

```json
{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "io-sylai-guardian": {
      "type": "remote",
      "url": "https://guardian.sylai.io/mcp",
      "enabled": true
    }
  }
}
```

### OpenClaw

```bash
openclaw mcp add io-sylai-guardian --url 'https://guardian.sylai.io/mcp' --transport streamable-http
```

### Hermes

```yaml
mcp_servers:
  io-sylai-guardian:
    url: "https://guardian.sylai.io/mcp"
```

### Netclaw

```json
{
  "McpServers": {
    "io-sylai-guardian": {
      "Transport": "http",
      "Url": "https://guardian.sylai.io/mcp"
    }
  }
}
```

### Vellum

```bash
assistant mcp add io-sylai-guardian -t streamable-http -u 'https://guardian.sylai.io/mcp'
```

### Other

```json
{
  "mcpServers": {
    "io-sylai-guardian": {
      "type": "http",
      "url": "https://guardian.sylai.io/mcp"
    }
  }
}
```

The mcpServers block is a cross-client convention. Remote transports vary, so check your client's docs.

## 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.

### 2026-11-05 (score 65, +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.

### 2026-11-02 (score 64, +1)

No change was recorded against any check on this day. Stability & Change Management went from 33 to 37. That category is still filling its 30-day observation window: 10 days of observed history at the previous scan, 11 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-31 (score 63, +1)

No change was recorded against any check on this day. Stability & Change Management went from 27 to 30. That category is still filling its 30-day observation window: 8 days of observed history at the previous scan, 9 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-29 (score 62, +1)

No change was recorded against any check on this day. Stability & Change Management went from 20 to 23. That category is still filling its 30-day observation window: 6 days of observed history at the previous scan, 7 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-28 (score 61, 0)

- [security] The server rewrote its instructions, which are the text every model session reads
- [security] Tool “guardian_review” rewrote its description, which is the text the model reads
- [functional regression] Schema quality: 462 → 786
- [cosmetic] “guardian_review” added an optional parameter “cate”
- [cosmetic] “guardian_review” added an optional parameter “config”
- [cosmetic] “guardian_review” added an optional parameter “estimator”
- [cosmetic] “guardian_review” added an optional parameter “seed”
- [cosmetic] “guardian_review” added an optional parameter “sensitivity”

### 2026-10-27 (score 61, +1)

No change was recorded against any check on this day. Stability & Change Management went from 13 to 17. That category is still filling its 30-day observation window: 4 days of observed history at the previous scan, 5 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-24 (score 60, +1)

No change was recorded against any check on this day. Stability & Change Management went from 3 to 7. That category is still filling its 30-day observation window: 1 days of observed history at the previous scan, 2 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-23 (score 59, −1)

- [security regression] HSTS header: pass → fail
- [security] The server rewrote its instructions, which are the text every model session reads
- [security] Tool “guardian_review” rewrote its description, which is the text the model reads
- [functional improvement] Schema quality: 584 → 462
- [functional improvement] Stability: unverified → 0.03
- [functional] Schema quality: good → excellent
- [functional] New tool “guardian_request_upload”
- [cosmetic] “guardian_review” added an optional parameter “dataset_id”

## MCP tools (2)

### `guardian_review` (~1163 tokens)

Sanity-check a causal claim ("cause drove effect") before acting on it.

Provide exactly one of ``csv`` (CSV text), ``data`` (list of row objects) or
\``dataset_id`` (a dataset uploaded via ``guardian_request_upload``; use this for
more than ~200 rows; single-use, deleted when reviewed) containing columns named by
\``cause`` and ``effect``. Returns a verdict --
\``pass`` (act), ``caution`` (act carefully), or ``hold`` (do not act; the effect
looks confounded or unsupported) -- with the naive correlational effect versus the
confounder-adjusted causal effect and its confidence interval, the confounders
adjusted for, a confidence score, a plain-English interpretation, and a
recommended action, plus the estimator used and the inferred causal DAG. All numbers
are deterministic statistics (never LLM-generated); the LLM may only choose an
estimator id from a fixed whitelist and write the interpretation prose.

Args:
    cause: Treatment column the claim says drives the outcome (e.g. "ad_spend").
    effect: Outcome column (e.g. "new_customers").
    csv: Dataset as CSV text (header row required).
    data: Dataset as a list of row records (alternative to ``csv``).
    dataset_id: ID returned by ``guardian_request_upload`` after uploading the CSV
        (alternative to ``csv``/``data``; for datasets above ~200 rows). Single-use:
        the dataset is deleted when reviewed, so re-upload to retry.
    known_confounders: Columns to adjust for; otherwise discovered automatically.
    context: Free-text business context, e.g. "Q3 promo evaluation".
    units: Display-only unit hints by column, e.g. {"ad_spend": "USD"}.
    step: A concrete treatment step (e.g. 1000 for a $1,000 spend increase) to
        restate the effect in business terms (cost per incremental outcome, ...).
    time_col: Column to order rows by for time series (autocorrelation-robust
        standard errors and adstock).
    adstock: Opt-in geometric-adstock transform for a lagged/carryover treatment.
    se:…

Input parameters:

- `adstock`
- `cate`
- `cause` (string, required)
- `config`
- `context`
- `csv`
- `data`
- `dataset_id`
- `effect` (string, required)
- `estimator`
- `known_confounders`
- `se` (string)
- `seed`
- `sensitivity` (boolean)
- `step`
- `test_design`
- `time_col`
- `units`

### `guardian_request_upload` (~173 tokens)

Get a pre-signed URL for uploading a large CSV (more than ~200 rows).

Use this instead of pasting rows into ``guardian_review``. Returns ``upload_url``,
\``dataset_id`` and a ready-to-run ``curl`` command: run it (replace ``data.csv``
with your file; gzip is accepted with ``Content-Encoding: gzip``), then call
\``guardian_review`` with ``dataset_id`` (and no ``csv``/``data``). The URL is
single-use and expires after 30 minutes; the dataset is only usable by the same API
key, and is single-use too: it is deleted when ``guardian_review`` reads it (even if
that review fails), so request a new upload to retry. This call does not consume
review quota.

## Diagnostics

Captured diagnostic sections: TLS, DNSSEC, Authorisation, Transports. The full working is on the page: https://verifymcp.io/servers/io-sylai-guardian/guardian#diagnostics

## Score history

- 2026-11-05: 65
- 2026-11-04: 64
- 2026-11-03: 64
- 2026-11-02: 64
- 2026-11-01: 63
- 2026-10-31: 63
- 2026-10-30: 62
- 2026-10-29: 62
- 2026-10-28: 61
- 2026-10-27: 61
- 2026-10-26: 60
- 2026-10-25: 60
- 2026-10-24: 60
- 2026-10-23: 59
- 2026-10-22: 60

## Common questions

### What is the Syl Guardian MCP server?

Syl Guardian is an MCP server listed in the public MCP registry as io.sylai/guardian. Causal check on AI agent claims, from ad-spend/ROAS lift to any decision: pass, caution or hold. This page covers its hosted endpoint (https://guardian.sylai.io/mcp).

### Is the Syl Guardian MCP server safe to use?

Syl Guardian scores 65 out of 100 on VerifyMCP. 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 Syl Guardian MCP server expose?

Syl Guardian exposes 2 tools: guardian_review, guardian_request_upload. Their descriptions and schemas cost roughly 1,336 tokens of context every time the server is loaded.

### Does the Syl Guardian MCP server require authentication?

No. We connected to Syl Guardian without credentials and it answered, so anything it exposes is reachable by anyone who knows the address.

### Is the Syl Guardian MCP server still maintained?

Syl Guardian 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.

## Links

- Remote endpoint: https://guardian.sylai.io/mcp
- Authorisation metadata: https://guardian.sylai.io/.well-known/oauth-protected-resource/mcp
- Repository: https://github.com/connor274/syl-guardian-mcp
- Website: https://sylai.io/guardian
- Changelog RSS feed: https://verifymcp.io/servers/io-sylai-guardian/guardian.xml
- Changelog JSON feed: https://verifymcp.io/servers/io-sylai-guardian/guardian.json
- HTML version of this page: https://verifymcp.io/servers/io-sylai-guardian/guardian