isitdns

Check a domain's DNS

check_domain

Read-onlyIdempotent

Check a domain that is not working: whether the name resolves in public DNS, then the eleven-check audit of its zone, each row ok, warn, fail or skipped with why. DNS only, not HTTP or TLS, and not for one record: dig. Measured from the isitdns edge and its probes, never the caller's network. from moves the recursion, TTL and UDP truncation rows to that region's probe.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`from`	No	Region of the probe for the recursion, TTL and UDP truncation rows
`name`	Yes	The domain to audit. Also as "domain"; a URL is read as its host.

Output Schema

TableJSON Schema

Name	Required	Description
`api`	Yes	The /api GET that asks it again, as a new reading
`checks`	No	The eleven rows: id, label, status, detail, receipt ids, and on a warn or fail row that has one, next: the one reading to take next (tool, args, command)
`summary`	No	Counts of ok, warn, fail and skip rows
`askAgain`	No	The isitdns.net page that asks it again, when one does
`receipts`	No	One per DNS read: what, of whom, from where, when, rcode, flags, EDE, ms, answer
`resolves`	No	The first line: state, the line, the receipt ids it rests on
`generatedAt`	No	When the audit ran

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedOct 15, 2026

changedOutput schema / properties / checks / description

Previous value: -"The eleven rows: id, label, status, detail, receipt ids"New value: +"The eleven rows: id, label, status, detail, receipt ids, and on a warn or fail row that has one, next: the one reading to take next (tool, args, command)"

Changed1 schema field changedOct 13, 2026

changedInput schema / properties / from / description

Previous value: -"Ask from the probe in this region"New value: +"Region of the probe for the recursion, TTL and UDP truncation rows"

Changed1 schema field changedOct 9, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "api": {
+      "description": "The /api GET that asks it again, as a new reading",
+      "type": "string"
+    },
+    "askAgain": {
+      "description": "The isitdns.net page that asks it again, when one does",
+      "type": "string"
+    },
+    "checks": {
+      "description": "The eleven rows: id, label, status, detail, receipt ids",
+      "type": "array"
+    },
+    "generatedAt": {
+      "description": "When the audit ran",
+      "type": "string"
+    },
+    "receipts": {
+      "description": "One per DNS read: what, of whom, from where, when, rcode, flags, EDE, ms, answer",
+      "type": "array"
+    },
+    "resolves": {
+      "description": "The first line: state, the line, the receipt ids it rests on",
+      "type": "object"
+    },
+    "summary": {
+      "description": "Counts of ok, warn, fail and skip rows",
+      "type": "object"
+    }
+  },
+  "required": [
+    "api"
+  ],
+  "type": "object"
+}

Changed2 schema fields changedSep 29, 2026

addedInput schema / properties / from

Added value: +{
+  "description": "Ask from the probe in this region",
+  "enum": [
+    "north-america",
+    "europe"
+  ],
+  "type": "string"
+}

changedInput schema / properties / name / description

Previous value: -"The domain to audit. Also accepted as \"domain\"; a URL is reduced to its host."New value: +"The domain to audit. Also as \"domain\"; a URL is read as its host."

Changed1 schema field changedSep 28, 2026

changedInput schema / properties / name / description

Previous value: -"The domain to audit"New value: +"The domain to audit. Also accepted as \"domain\"; a URL is reduced to its host."

First observedSep 10, 2026

TDQS

A4.3/5.0

Behavior4/5

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

Annotations already cover safety (readOnly, idempotent, non-destructive, openWorld), so the description's job is added context, and it delivers: results are measured from the isitdns edge and its probes rather than the caller's network, and 'from' relocates only the recursion, TTL and UDP truncation rows. It does not describe result aggregation or failure modes, but an output schema exists to carry return shape.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Dense but front-loaded: the core operation and exclusions come first, with the probe-region nuance last. The compressed phrasing ('not for one record: dig', 'from moves the ... rows') is efficient, though the run-on clauses demand a second read.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a read-only audit tool with an output schema, annotations and full parameter coverage, the description supplies the scope, the measurement vantage point, and the row semantics. Only the shape of the summary/worst-case outcome is left implicit, which the output schema plausibly covers.

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 both parameters are documented there, so the baseline is 3. The description restates the 'from' behaviour (recursion/TTL/UDP truncation rows) already present in the schema and adds no new format or alias detail for 'name'.

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 precise verb and resource: resolve a name in public DNS plus an eleven-check audit of the zone, returning per-row ok/warn/fail/skipped. It explicitly carves itself away from dig ('not for one record') and from HTTP/TLS work, so an agent can distinguish it from siblings 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 Guidelines5/5

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

Gives the triggering condition ('a domain that is not working'), the explicit exclusions (DNS only, not HTTP or TLS), and names the alternative for the single-record case ('dig'). This is the when/when-not/alternative triad in two sentences.

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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