tools_reverse_ip_lookupFree public API. Reverse-DNS (PTR) lookup for an IP address. Returns one or more hostnames if configured.
| Name | Required | Description | Default |
|---|---|---|---|
| ip | Yes | IPv4 or IPv6 address, e.g. 8.8.8.8. |
| Name | Required | Description | Default |
|---|---|---|---|
| ok | Yes | Always true here; failures return an isError result instead. | |
| data | Yes |
Changes observed during successful MCP inspections.
Output schema / (root)Previous value: -nullNew value: +{
+ "$schema": "http://json-schema.org/draft-07/schema#",
+ "additionalProperties": true,
+ "description": "PTR hostnames for the IP, plus co-hosted domains when available.",
+ "properties": {
+ "data": {
+ "additionalProperties": true,
+ "properties": {
+ "hostnames": {
+ "description": "PTR records.",
+ "items": {
+ "type": "string"
+ },
+ "type": "array"
+ },
+ "ip": {
+ "type": "string"
+ },
+ "ptrError": {
+ "type": [
+ "string",
+ "null"
+ ]
+ },
+ "sharedHosts": {
+ "anyOf": [
+ {
+ "items": {
+ "type": "string"
+ },
+ "type": "array"
+ },
+ {
+ "type": "null"
+ }
+ ],
+ "description": "Other hostnames on this IP; null when unavailable."
+ },
+ "sharedHostsNote": {
+ "type": [
+ "string",
+ "null"
+ ]
+ },
+ "sharedHostsSource": {
+ "type": [
+ "string",
+ "null"
+ ]
+ },
+ "sharedHostsStatus": {
+ "description": "ok | unavailable | error.",
+ "type": "string"
+ },
+ "sharedHostsTotal": {
+ "type": [
+ "number",
+ "null"
+ ]
+ },
+ "sharedHostsTruncated": {
+ "type": [
+ "boolean",
+ "null"
+ ]
+ }
+ },
+ "required": [
+ "ip",
+ "hostnames"
+ ],
+ "type": "object"
+ },
+ "ok": {
+ "description": "Always true here; failures return an isError result instead.",
+ "type": "boolean"
+ }
+ },
+ "required": [
+ "ok",
+ "data"
+ ],
+ "type": "object"
+}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 still adds value by flagging it as a free public API and warning that hostnames are returned only 'if configured,' which telegraphs a possible empty result.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Three short sentences, front-loaded with the core purpose and followed by the return contract. No padding or redundancy.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
An output schema exists, so return values need no further explanation, and the description covers the essential scope. The only minor gap is the absence of any when-to-use framing against the many sibling DNS tools.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
There is a single parameter and schema description coverage is 100%, with the schema already specifying IPv4/IPv6 and giving an example. The description adds no format or syntax detail beyond that, so the baseline 3 applies.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
States a specific verb and resource — a reverse-DNS (PTR) lookup keyed on an IP address — and explicitly notes it returns hostnames. This cleanly separates it from the forward-DNS siblings (cname_lookup, dns_record_lookup, txt_record_lookup) without needing their schemas.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description implies usage (resolve an IP back to hostnames) but never states when to reach for this versus dns_record_lookup or cname_lookup, nor any conditions or exclusions. The 'Free public API' note gives context but not selection guidance.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.