Uptimeify

mx_lookup

Read-only

Look up a domain's MX records and resolve each mail exchanger to its IPv4 and IPv6 addresses, ordered by priority and flagged when a host resolves into private address space. Tells you where mail for the domain is delivered; it does not connect to those servers, does not test SMTP, and says nothing about whether the domain is authorised to send (spf_check, dkim_check, dmarc_check). Anonymous and rate-limited per IP.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`domain`	Yes	Domain name, e.g. deinkunde.com

Output Schema

TableJSON Schema

Name	Required	Description	Default
`ok`	No
`found`	No
`domain`	No
`servers`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed7 schema fields changedSep 11, 2026

removedOutput schema / properties / domain / anyOf

Removed value: -[
-  {
-    "type": "string"
-  },
-  {
-    "type": "null"
-  }
-]

addedOutput schema / properties / domain / type
```
Added value: +[
+  "string",
+  "null"
+]
```

removedOutput schema / properties / found / anyOf

Removed value: -[
-  {
-    "type": "boolean"
-  },
-  {
-    "type": "null"
-  }
-]

addedOutput schema / properties / found / type
```
Added value: +[
+  "boolean",
+  "null"
+]
```

removedOutput schema / properties / ok / anyOf

Removed value: -[
-  {
-    "type": "boolean"
-  },
-  {
-    "type": "null"
-  }
-]

addedOutput schema / properties / ok / type

Added value: +[
+  "boolean",
+  "null"
+]

changedOutput schema / properties / servers / anyOf

Previous value: -[
-  {
-    "items": {
-      "additionalProperties": {},
-      "properties": {
-        "exchange": {
-          "anyOf": [
-            {
-              "type": "string"
-            },
-            {
-              "type": "null"
-            }
-          ]
-        },
-        "ipv4": {
-          "anyOf": [
-            {
-              "items": {
-                "type": "string"
-              },
-              "type": "array"
-            },
-            {
-              "type": "null"
-            }
-          ]
-        },
-        "ipv6": {
-          "anyOf": [
-            {
-              "items": {
-                "type": "string"
-              },
-              "type": "array"
-            },
-            {
-              "type": "null"
-            }
-          ]
-        },
-        "priority": {
-          "anyOf": [
-            {
-              "type": "number"
-            },
-            {
-              "type": "null"
-            }
-          ]
-        },
-        "private": {
-          "anyOf": [
-            {
-              "type": "boolean"
-            },
-            {
-              "type": "null"
-            }
-          ]
-        }
-      },
-      "type": "object"
-    },
-    "type": "array"
-  },
-  {
-    "type": "null"
-  }
-]New value: +[
+  {
+    "items": {
+      "additionalProperties": {},
+      "properties": {
+        "exchange": {
+          "type": [
+            "string",
+            "null"
+          ]
+        },
+        "ipv4": {
+          "anyOf": [
+            {
+              "items": {
+                "type": "string"
+              },
+              "type": "array"
+            },
+            {
+              "type": "null"
+            }
+          ]
+        },
+        "ipv6": {
+          "anyOf": [
+            {
+              "items": {
+                "type": "string"
+              },
+              "type": "array"
+            },
+            {
+              "type": "null"
+            }
+          ]
+        },
+        "priority": {
+          "type": [
+            "number",
+            "null"
+          ]
+        },
+        "private": {
+          "type": [
+            "boolean",
+            "null"
+          ]
+        }
+      },
+      "type": "object"
+    },
+    "type": "array"
+  },
+  {
+    "type": "null"
+  }
+]

Changed1 schema field changedAug 4, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "additionalProperties": {},
+  "properties": {
+    "domain": {
+      "anyOf": [
+        {
+          "type": "string"
+        },
+        {
+          "type": "null"
+        }
+      ]
+    },
+    "found": {
+      "anyOf": [
+        {
+          "type": "boolean"
+        },
+        {
+          "type": "null"
+        }
+      ]
+    },
+    "ok": {
+      "anyOf": [
+        {
+          "type": "boolean"
+        },
+        {
+          "type": "null"
+        }
+      ]
+    },
+    "servers": {
+      "anyOf": [
+        {
+          "items": {
+            "additionalProperties": {},
+            "properties": {
+              "exchange": {
+                "anyOf": [
+                  {
+                    "type": "string"
+                  },
+                  {
+                    "type": "null"
+                  }
+                ]
+              },
+              "ipv4": {
+                "anyOf": [
+                  {
+                    "items": {
+                      "type": "string"
+                    },
+                    "type": "array"
+                  },
+                  {
+                    "type": "null"
+                  }
+                ]
+              },
+              "ipv6": {
+                "anyOf": [
+                  {
+                    "items": {
+                      "type": "string"
+                    },
+                    "type": "array"
+                  },
+                  {
+                    "type": "null"
+                  }
+                ]
+              },
+              "priority": {
+                "anyOf": [
+                  {
+                    "type": "number"
+                  },
+                  {
+                    "type": "null"
+                  }
+                ]
+              },
+              "private": {
+                "anyOf": [
+                  {
+                    "type": "boolean"
+                  },
+                  {
+                    "type": "null"
+                  }
+                ]
+              }
+            },
+            "type": "object"
+          },
+          "type": "array"
+        },
+        {
+          "type": "null"
+        }
+      ]
+    }
+  },
+  "type": "object"
+}

First observedAug 4, 2026

TDQS

A4.7/5.0

Behavior5/5

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

Annotations only declare readOnlyHint=true; the description adds substantive traits beyond that: anonymous access, per-IP rate limiting, no connection to the discovered hosts, and result characteristics (priority ordering, private-address-space flagging). These are exactly the operational constraints an agent needs before calling.

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?

Two densely packed sentences with zero filler; the positive capability is front-loaded and the exclusions follow immediately. Every clause carries routing or behavioural information.

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 present, return values need not be described; the description instead covers the things the schema cannot — access model, rate limits, and non-capabilities. Nothing needed to call this tool correctly is missing.

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?

The single 'domain' parameter is fully documented in the schema (100% coverage) and the description only implies it via 'a domain's MX records'. No additional syntax, format or validation meaning is added, so the baseline 3 for high schema coverage applies.

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?

Specific verb (look up) plus resource (a domain's MX records), with explicit scope: resolves each exchanger to IPv4/IPv6, ordered by priority, flags private address space. It also demarcates itself from siblings by naming spf_check, dkim_check and dmarc_check as the tools that answer sending-authorisation questions.

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 both when-to-use (finding where mail for a domain is delivered) and when-not: it does not connect to servers, does not test SMTP, and says nothing about sending authorisation. The alternatives for that latter need are named explicitly, so an agent can route correctly without 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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