> ## Documentation Index
> Fetch the complete documentation index at: https://docs.vms.verolabs.co/llms.txt
> Use this file to discover all available pages before exploring further.

# Probe: tls_cert

> Monitor TLS certificate expiry

## Description

The `tls_cert` probe connects to a host via TLS, reads the leaf certificate, and calculates days remaining before expiry. Supports warning and critical thresholds.

Certificate verification is intentionally disabled — the probe reads expired or self-signed certificates to report accurate days remaining.

## Config fields

| Field          | Type     | Required | Default | Description                                                      |
| -------------- | -------- | -------- | ------- | ---------------------------------------------------------------- |
| `type`         | `string` | Yes      | —       | Must be `"tls_cert"`                                             |
| `host`         | `string` | Yes      | —       | Host for TLS connection and SNI                                  |
| `port`         | `int`    | Yes      | —       | TLS port (1–65535)                                               |
| `warningDays`  | `int`    | No       | `0`     | Days remaining threshold for `warning`. `0` = no warning         |
| `criticalDays` | `int`    | No       | `0`     | Days remaining threshold for `critical`. `0` = no critical alert |

<Warning>
  If both `warningDays` and `criticalDays` are > 0, `criticalDays` must be ≤ `warningDays`.
</Warning>

## Metrics

| Metric                        | Type  | Unit | Description                                          |
| ----------------------------- | ----- | ---- | ---------------------------------------------------- |
| `vms.tls_cert.days_remaining` | gauge | days | Days until cert expiry. `-1` if TLS handshake failed |

## Example config

```json theme={null}
{
  "type": "tls_cert",
  "host": "app.verolabs.co",
  "port": 443,
  "warningDays": 30,
  "criticalDays": 7
}
```