Uptimeify

Reverse DNS

reverse_dns

Read-only

Resolves a public IP address to the PTR hostnames published for it, or returns 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; a missing PTR is common and not a fault. Forward and reverse records need not agree, and this call does not check that they do. Anonymous, rate-limited per IP.

Input Schema

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

Output 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

A4.3/5.0

Behavior5/5

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

Annotations already declare readOnlyHint=true and openWorldHint=true, but the description adds meaningful behavior beyond them: anonymous access, per-IP rate limiting, and the failure mode of returning the resolver's error when no PTR exists. The PTR provenance caveat ('set by whoever controls the address block') further sets correct expectations about result semantics.

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?

The description is front-loaded with the core action, then adds only caveats that prevent misinterpretation. Every sentence earns its place; no redundant restatement of the name or schema.

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?

For a single-parameter, read-only lookup with an output schema and safety annotations already in place, the description supplies the remaining interpretive context (PTR ownership, missing PTR normality, no forward/reverse check, rate limiting). Nothing required for correct invocation 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 coverage is 100% for the single 'ip' parameter, and its description already specifies 'Public IPv4 or IPv6 address.' The tool description adds no syntax or format detail beyond the schema, so the baseline of 3 is appropriate for a fully documented single parameter.

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 (resolves) and resource (public IP to PTR hostnames) and clarifies the reverse-only scope with 'Forward and reverse records need not agree, and this call does not check that they do,' which distinguishes it from forward DNS siblings like check_dns. An agent can tell what this tool does without reading 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?

The description gives implied usage (a reverse DNS lookup) and interpretation guidance ('a missing PTR is common and not a fault'), but never states when to choose it over alternatives such as check_dns or dns_propagation. It lacks explicit when-to-use or when-not-to-use 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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