RunStack Checks

DNS lookup across resolvers

check_dns

Read-onlyIdempotent

Resolve a name at several public resolvers (Google, Cloudflare, Quad9, …) and compare their answers. Use after changing DNS records to check propagation, or when some users reach a different IP or get NXDOMAIN. Use check_email_domain instead for SPF/DKIM/DMARC analysis. Returns per-resolver answers, inconsistencies and a verdict.

Input Schema

Name	Required	Description	Default
`type`	No	Record type to query. ALL queries the common types at once. Default ALL.	ALL
`domain`	Yes	Domain or hostname to resolve, e.g. www.example.com

Output Schema

Name	Required	Description
`ok`	Yes	false when the check could not run (see error / message)
`tool`	No
`error`	No	Error code when ok is false
`facts`	No
`notice`	No	Usage note, e.g. anonymous-tier limits
`target`	No	What was checked
`message`	No
`verdict`	No
`findings`	No
`headline`	No	One-line summary
`reportUrl`	No	Shareable report link

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedOct 18, 2026

addedOutput schema / properties / notice

Added value: +{
+  "description": "Usage note, e.g. anonymous-tier limits",
+  "type": "string"
+}

Changed5 schema fields changedOct 18, 2026

addedInput schema / additionalProperties
```
Added value: +false
```

changedInput schema / properties / domain / description

Previous value: -"Domain name"New value: +"Domain or hostname to resolve, e.g. www.example.com"

addedInput schema / properties / type / default
```
Added value: +"ALL"
```

changedInput schema / properties / type / description

Previous value: -"Record type"New value: +"Record type to query. ALL queries the common types at once. Default ALL."

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "error": {
+      "description": "Error code when ok is false",
+      "type": "string"
+    },
+    "facts": {
+      "items": {
+        "properties": {
+          "label": {
+            "type": "string"
+          },
+          "value": {
+            "type": "string"
+          }
+        },
+        "required": [
+          "label",
+          "value"
+        ],
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "findings": {
+      "items": {
+        "properties": {
+          "code": {
+            "type": "string"
+          },
+          "detail": {
+            "description": "Why it matters / cause",
+            "type": "string"
+          },
+          "docs": {
+            "description": "How-to article URL",
+            "type": "string"
+          },
+          "fix": {
+            "description": "How to fix",
+            "type": "string"
+          },
+          "severity": {
+            "enum": [
+              "error",
+              "warning",
+              "info",
+              "ok"
+            ],
+            "type": "string"
+          },
+          "title": {
+            "type": "string"
+          }
+        },
+        "required": [
+          "severity",
+          "title"
+        ],
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "headline": {
+      "description": "One-line summary",
+      "type": "string"
+    },
+    "message": {
+      "type": "string"
+    },
+    "ok": {
+      "description": "false when the check could not run (see error / message)",
+      "type": "boolean"
+    },
+    "reportUrl": {
+      "description": "Shareable report link",
+      "type": "string"
+    },
+    "target": {
+      "description": "What was checked",
+      "type": "string"
+    },
+    "tool": {
+      "type": "string"
+    },
+    "verdict": {
+      "enum": [
+        "ok",
+        "warn",
+        "fail"
+      ],
+      "type": "string"
+    }
+  },
+  "required": [
+    "ok"
+  ],
+  "type": "object"
+}

First observedOct 17, 2026

TDQS

A4.5/5.0

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 safety is covered; the description adds the meaningful behavioral context that queries fan out to multiple third-party resolvers and the result compares them for inconsistencies with a verdict. It stops short of noting rate limits, resolver timeouts, or caching caveats.

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, zero waste, and the core behavior is front-loaded ahead of the usage triggers and the sibling exclusion. Every sentence earns its place.

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 restated, and the description covers purpose, triggers, alternative tool, and comparison behavior for a simple two-parameter read tool. Nothing an agent needs to invoke it 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%, so both parameters (domain and the record-type enum with ALL default) are already fully documented in the schema. The description adds no syntax or format detail beyond that, which is the expected baseline when the schema does the heavy lifting.

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/compare) and resource (a name across several named public resolvers), and explicitly distinguishes itself from the sibling check_email_domain. An agent can tell what this tool does and what it is not 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 Guidelines5/5

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

Gives concrete when-to-use triggers (after DNS record changes to check propagation, when users see a different IP or NXDOMAIN) and names the alternative tool with the condition that selects it (SPF/DKIM/DMARC analysis). Nothing is left to 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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