RunStack Checks

TLS / certificate check

check_tls

Read-onlyIdempotent

Scan a public host's TLS from the internet: certificate validity, chain completeness, expiry date, hostname match, enabled protocols (TLS 1.0–1.3), cipher suites, HSTS. Use when browsers show certificate errors, before/after renewing or rotating a certificate, or to confirm old TLS versions are disabled. Use this (not check_http) for anything about the certificate or TLS configuration itself; works on any TLS port, not only 443. Returns a verdict, findings with cause and fix, and a shareable report link. Takes up to ~60 s.

Input Schema

Name	Required	Description	Default
`host`	Yes	Public hostname to scan, without scheme or path, e.g. example.com
`port`	No	TLS port, e.g. 443 (HTTPS), 465 (SMTPS), 993 (IMAPS). Default 443.

Output Schema

Name	Required	Description
`ok`	Yes	false when the check could not run (see error / message)
`tool`	No
`error`	No	Error code when ok is false
`facts`	No
`notice`	No	Usage note, e.g. anonymous-tier limits
`target`	No	What was checked
`message`	No
`verdict`	No
`findings`	No
`headline`	No	One-line summary
`reportUrl`	No	Shareable report link

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedOct 18, 2026

addedOutput schema / properties / notice

Added value: +{
+  "description": "Usage note, e.g. anonymous-tier limits",
+  "type": "string"
+}

Changed7 schema fields changedOct 18, 2026

addedInput schema / additionalProperties
```
Added value: +false
```

changedInput schema / properties / host / description

Previous value: -"Public hostname, e.g. example.com"New value: +"Public hostname to scan, without scheme or path, e.g. example.com"

addedInput schema / properties / port / default
```
Added value: +443
```

changedInput schema / properties / port / description

Previous value: -"TLS port (default 443)"New value: +"TLS port, e.g. 443 (HTTPS), 465 (SMTPS), 993 (IMAPS). Default 443."

addedInput schema / properties / port / maximum
```
Added value: +65535
```
addedInput schema / properties / port / minimum
```
Added value: +1
```

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "error": {
+      "description": "Error code when ok is false",
+      "type": "string"
+    },
+    "facts": {
+      "items": {
+        "properties": {
+          "label": {
+            "type": "string"
+          },
+          "value": {
+            "type": "string"
+          }
+        },
+        "required": [
+          "label",
+          "value"
+        ],
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "findings": {
+      "items": {
+        "properties": {
+          "code": {
+            "type": "string"
+          },
+          "detail": {
+            "description": "Why it matters / cause",
+            "type": "string"
+          },
+          "docs": {
+            "description": "How-to article URL",
+            "type": "string"
+          },
+          "fix": {
+            "description": "How to fix",
+            "type": "string"
+          },
+          "severity": {
+            "enum": [
+              "error",
+              "warning",
+              "info",
+              "ok"
+            ],
+            "type": "string"
+          },
+          "title": {
+            "type": "string"
+          }
+        },
+        "required": [
+          "severity",
+          "title"
+        ],
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "headline": {
+      "description": "One-line summary",
+      "type": "string"
+    },
+    "message": {
+      "type": "string"
+    },
+    "ok": {
+      "description": "false when the check could not run (see error / message)",
+      "type": "boolean"
+    },
+    "reportUrl": {
+      "description": "Shareable report link",
+      "type": "string"
+    },
+    "target": {
+      "description": "What was checked",
+      "type": "string"
+    },
+    "tool": {
+      "type": "string"
+    },
+    "verdict": {
+      "enum": [
+        "ok",
+        "warn",
+        "fail"
+      ],
+      "type": "string"
+    }
+  },
+  "required": [
+    "ok"
+  ],
+  "type": "object"
+}

First observedOct 17, 2026

TDQS

A4.7/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already cover the safety profile (readOnly, idempotent, openWorld, non-destructive), but the description adds genuine operational context: the scan takes up to ~60 s and works on any TLS port, not just 443. The return summary is partially redundant with the output schema, which keeps this from a 5.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with the scan scope, then usage, then routing exclusion, then output and timing. Every sentence carries distinct information with no filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With an output schema and rich annotations present, the description only needs to add scope, routing, timing and port flexibility, all of which it provides. An agent has everything needed to select and call this correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the schema already documents host and port, giving a baseline of 3. The description adds meaning beyond the schema by noting it works on any TLS port rather than only 443, reinforcing the port parameter's intended flexibility.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (scan) and resource (public host's TLS) and enumerates exactly what is inspected: certificate validity, chain completeness, expiry, hostname match, protocols, cipher suites, HSTS. It explicitly names the sibling it is not (check_http), so an agent can route without opening either schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives three concrete trigger scenarios (browser certificate errors, before/after renew or rotation, confirming old TLS versions are disabled) and an explicit exclusion routing certificate/TLS-config questions away from check_http. Nothing is left to inference.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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