BlackVeil DNS & Email Security Scanner

check_dane

Read-onlyIdempotent

Check DANE/TLSA certificate pinning for SMTP at port 25. Resolves the domain's MX hosts and looks up TLSA records at _25._tcp., validating their syntax, usage/selector/matching-type fields and DNSSEC backing on the MX host's zone. The record is reported as present but UNVERIFIED: there is no certificate probe for port 25/SMTP, so the pinned data is never compared against the certificate the mail server actually serves (the comparable capture-and-compare pipeline exists only for check_dane_https at port 443, and is itself currently kill-switched there — see that tool's description). Use when asked if SMTP mail servers publish DANE/TLSA pinning; this does not confirm the pin matches the live certificate. For HTTPS DANE at port 443, use check_dane_https instead. Part of the scan_domain audit.

Input Schema

TableJSON Schema

Name	Required	Description
`domain`	Yes	Domain to check (e.g., example.com)
`format`	No	Output verbosity. Auto-detected if omitted.
`force_refresh`	No	Bypass cache and run a fresh check. Useful after DNS changes.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`score`	Yes
`passed`	Yes
`partial`	No
`category`	Yes
`findings`	Yes
`checkStatus`	No
`verdictWithheld`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedOct 5, 2026
- addedOutput schema / properties / verdictWithheld
```
Added value: +{
+  "type": "boolean"
+}
```
Changed2 schema fields changedAug 18, 2026
- addedOutput schema / properties / checkStatus
```
Added value: +{
+  "type": "string"
+}
```
- addedOutput schema / properties / partial
```
Added value: +{
+  "type": "boolean"
+}
```

Changed1 schema field changedJul 2, 2026

addedInput schema / properties / force_refresh

Added value: +{
+  "description": "Bypass cache and run a fresh check. Useful after DNS changes.",
+  "type": "boolean"
+}

Changed1 schema field changedMay 26, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "additionalProperties": {},
+  "properties": {
+    "category": {
+      "type": "string"
+    },
+    "findings": {
+      "items": {
+        "additionalProperties": {},
+        "properties": {},
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "passed": {
+      "type": "boolean"
+    },
+    "score": {
+      "type": "number"
+    }
+  },
+  "required": [
+    "category",
+    "score",
+    "passed",
+    "findings"
+  ],
+  "type": "object"
+}

First observedApr 21, 2026

TDQS

A4.6/5.0

Behavior5/5

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

Goes well beyond the readOnly/idempotent/openWorld annotations by disclosing a critical behavioral caveat: the record is reported as present but UNVERIFIED because there is no port 25 certificate probe, so pinned data is never compared to the served certificate. It also notes the comparable HTTPS pipeline is kill-switched. This is exactly the kind of non-obvious limitation an agent cannot infer from annotations.

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?

Front-loads purpose and mechanism before the caveat, and every sentence carries weight. The parenthetical about the kill-switched HTTPS pipeline is slightly tangential for this tool but supports the UNVERIFIED claim, so it is defensible rather than wasteful.

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 a rich annotation set and an output schema present, the description fills the remaining gap — the verification limitation — completely. An agent knows what it does, what it returns conceptually, and what it cannot confirm.

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 all three parameters (domain, format enum, force_refresh) are documented in the schema itself. The description adds no parameter-level syntax or defaults, 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 (Check) and resource (DANE/TLSA certificate pinning for SMTP at port 25), and precisely scopes the mechanism: MX resolution plus TLSA lookup at _25._tcp.<mx-host>. It explicitly distinguishes itself from check_dane_https for HTTPS at port 443, so an agent can separate it from its nearest sibling.

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?

Explicitly states when to use it ('Use when asked if SMTP mail servers publish DANE/TLSA pinning') and when not to ('this does not confirm the pin matches the live certificate'), and names the correct alternative for the HTTPS case. Routing is unambiguous.

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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