Uptimeify

reverse_dns

Read-only

Resolve a public IP address to the PTR hostnames published for it, returning every name the pointer record carries, or the resolver's error where there is none. A PTR is set by whoever controls the address block, so it names the host rather than necessarily the site running on it, and a missing PTR is common and not a fault. It is not the inverse of check_dns: a forward record and a PTR need not agree, and this call does not verify that they do. Anonymous and rate-limited per IP.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`ip`	Yes	Public IPv4 or IPv6 address

Output Schema

TableJSON Schema

Name	Required	Description	Default
`ip`	No
`ok`	No
`error`	No
`hostnames`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed6 schema fields changedSep 11, 2026

removedOutput schema / properties / error / anyOf

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

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

removedOutput schema / properties / ip / anyOf

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

addedOutput schema / properties / ip / type

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

removedOutput schema / properties / ok / anyOf

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

addedOutput schema / properties / ok / type

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

Changed1 schema field changedAug 4, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "additionalProperties": {},
+  "properties": {
+    "error": {
+      "anyOf": [
+        {
+          "type": "string"
+        },
+        {
+          "type": "null"
+        }
+      ]
+    },
+    "hostnames": {
+      "anyOf": [
+        {
+          "items": {
+            "type": "string"
+          },
+          "type": "array"
+        },
+        {
+          "type": "null"
+        }
+      ]
+    },
+    "ip": {
+      "anyOf": [
+        {
+          "type": "string"
+        },
+        {
+          "type": "null"
+        }
+      ]
+    },
+    "ok": {
+      "anyOf": [
+        {
+          "type": "boolean"
+        },
+        {
+          "type": "null"
+        }
+      ]
+    }
+  },
+  "type": "object"
+}

First observedAug 4, 2026

TDQS

A4.5/5.0

Behavior5/5

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

Beyond the readOnlyHint annotation, it discloses the auth profile (anonymous), a rate limit scoped per IP, the failure mode (returns the resolver's error where there is none), and an important interpretive caveat (a PTR names the host, not necessarily the site). This is unusually rich behavioral context for a read-only call.

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 sentences with no filler: the operation leads, the interpretive caveat and the sibling disambiguation follow, and operational constraints close. Every sentence carries distinct 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?

Output schema covers return values, so the description correctly omits them and instead covers the two things the schema cannot: the rate limit and the fact that a null/error result is expected rather than a failure. Nothing needed to call this 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?

Schema description coverage is 100% and the single 'ip' parameter is already documented as a public IPv4 or IPv6 address. The description restates 'public IP address' without adding format, validation, or edge-case detail, so the baseline 3 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?

States a specific verb (Resolve) and resource (public IP address to PTR hostnames), and explicitly distinguishes itself from the sibling check_dns by noting it is not its inverse. An agent can pick it apart from check_dns and dns_propagation without opening any schema.

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

Usage Guidelines4/5

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

Gives clear context for when results are meaningful ('a missing PTR is common and not a fault') and rules out the check_dns inverse assumption. It does not name an explicit alternative to use instead when reverse DNS is inappropriate, so it stops short of full when/when-not routing.

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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