domainee

SSL Certificate Check

tools_ssl_check

Read-onlyIdempotent

Free public API. Check the TLS certificate of any public hostname. Returns issuer, subject, validity dates, days until expiry, full chain, cipher, protocol, and SAN list. No Bearer required.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`host`	Yes	Hostname to check. Optionally with port, e.g. example.com:443.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`ok`	Yes	Always true here; failures return an isError result instead.
`data`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedSep 28, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "additionalProperties": true,
+  "description": "TLS certificate details for the host.",
+  "properties": {
+    "data": {
+      "additionalProperties": true,
+      "properties": {
+        "altNames": {
+          "description": "Subject Alternative Names (hostnames the cert covers).",
+          "items": {
+            "type": "string"
+          },
+          "type": "array"
+        },
+        "authorizationError": {
+          "description": "Why validation failed, e.g. CERT_HAS_EXPIRED.",
+          "type": [
+            "string",
+            "null"
+          ]
+        },
+        "authorized": {
+          "description": "Chain validates against public roots and matches the hostname.",
+          "type": "boolean"
+        },
+        "chain": {
+          "description": "Leaf first, then intermediates and root.",
+          "items": {
+            "additionalProperties": true,
+            "properties": {
+              "issuer": {
+                "$ref": "#/properties/data/properties/subject"
+              },
+              "subject": {
+                "$ref": "#/properties/data/properties/subject"
+              },
+              "validFrom": {
+                "type": "string"
+              },
+              "validTo": {
+                "type": "string"
+              }
+            },
+            "required": [
+              "subject",
+              "issuer",
+              "validFrom",
+              "validTo"
+            ],
+            "type": "object"
+          },
+          "type": "array"
+        },
+        "cipher": {
+          "anyOf": [
+            {
+              "additionalProperties": true,
+              "properties": {
+                "name": {
+                  "type": "string"
+                },
+                "version": {
+                  "type": "string"
+                }
+              },
+              "type": "object"
+            },
+            {
+              "type": "null"
+            }
+          ]
+        },
+        "daysUntilExpiry": {
+          "description": "Negative once expired.",
+          "type": "number"
+        },
+        "expired": {
+          "type": "boolean"
+        },
+        "fingerprint256": {
+          "type": "string"
+        },
+        "host": {
+          "type": "string"
+        },
+        "issuer": {
+          "$ref": "#/properties/data/properties/subject"
+        },
+        "port": {
+          "type": "number"
+        },
+        "protocol": {
+          "description": "Negotiated TLS version, e.g. TLSv1.3.",
+          "type": [
+            "string",
+            "null"
+          ]
+        },
+        "pubkeyBits": {
+          "type": "number"
+        },
+        "serialNumber": {
+          "type": "string"
+        },
+        "signatureAlgorithm": {
+          "type": "string"
+        },
+        "subject": {
+          "additionalProperties": true,
+          "properties": {
+            "C": {
+              "type": "string"
+            },
+            "CN": {
+              "type": "string"
+            },
+            "L": {
+              "type": "string"
+            },
+            "O": {
+              "type": "string"
+            },
+            "OU": {
+              "type": "string"
+            },
+            "ST": {
+              "type": "string"
+            }
+          },
+          "type": "object"
+        },
+        "validFrom": {
+          "description": "ISO 8601.",
+          "type": "string"
+        },
+        "validTo": {
+          "description": "ISO 8601.",
+          "type": "string"
+        }
+      },
+      "required": [
+        "host",
+        "port",
+        "authorized",
+        "expired",
+        "daysUntilExpiry",
+        "subject",
+        "issuer",
+        "validFrom",
+        "validTo",
+        "altNames",
+        "chain"
+      ],
+      "type": "object"
+    },
+    "ok": {
+      "description": "Always true here; failures return an isError result instead.",
+      "type": "boolean"
+    }
+  },
+  "required": [
+    "ok",
+    "data"
+  ],
+  "type": "object"
+}

First observedJul 19, 2026

TDQS

A4/5.0

Behavior4/5

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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds genuinely useful context beyond them: it is a free public API requiring no Bearer auth, which an agent needs in order to invoke it without configuring credentials. It stops short of noting rate limits or failure behavior for unreachable/invalid hosts.

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?

Three short sentences, each earning its place: capability, return contents, and auth requirement, with the core verb front-loaded. No filler or repetition.

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

Completeness4/5

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

With an output schema present, the enumerated return fields (issuer, chain, cipher, SAN list) are somewhat redundant, but nothing an agent needs to call the tool correctly is missing — the auth-free access and public-host constraint are both stated. Minor gap: no mention of behavior for non-TLS or unreachable hosts.

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

Parameters3/5

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

Schema coverage is 100% and the schema itself documents the optional port syntax (example.com:443), so the baseline is 3. The description contributes only the 'public hostname' constraint, which is a mild addition over the schema but no format or edge-case detail.

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 and resource ('Check the TLS certificate of any public hostname') and immediately scopes it to public hostnames, which cleanly separates it from DNS-record siblings like tools_dns_record_lookup or tools_cname_lookup. An agent can select it without opening the schema.

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

Usage Guidelines3/5

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

Usage is implied by the resource type (TLS certificate inspection) and the 'public hostname' scoping, but there is no explicit when-to-use, when-not-to-use, or named alternative among the many DNS/domain siblings. The auth note ('No Bearer required') is operational context rather than routing guidance.

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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