BlackVeil DNS & Email Security Scanner

check_dkim

Read-onlyIdempotent

Look up DKIM records for a domain. Probes common selectors, validates the signing algorithm used for outgoing email (RSA-1024/2048, Ed25519), and reports key strength. Use to verify that outbound email signatures are cryptographically sound. 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.
`selector`	No	DKIM selector. Omit to probe common ones.
`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

A4.2/5.0

Behavior4/5

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

Annotations already declare readOnly/openWorld/idempotent, so the safety profile is covered. The description adds genuine behavioral context beyond that: it probes common selectors automatically, validates the signing algorithm (RSA-1024/2048, Ed25519) and reports key strength. It doesn't mention cache behavior despite a force_refresh param, but the added context is substantive.

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?

Four compact sentences, purpose-first, each carrying a distinct payload (what it does, what it validates, when to use it, where it fits). No filler or redundancy.

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?

With an output schema present, return values need not be explained, and annotations carry the safety profile; the description supplies purpose, behavior, and audit context. It is nearly complete for a read-only probe, only lacking failure/error expectations or DNS-resolution caveats an agent might want.

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 the schema already documents domain, format, selector, and force_refresh. The description's mention of probing "common selectors" lightly contextualizes the selector param but adds no syntax or format meaning beyond the schema. Baseline 3 is appropriate.

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 (look up) and resource (DKIM records) scoped to a domain, and immediately differentiates itself from the email-auth siblings (check_spf, check_dmarc, check_bimi) by naming DKIM explicitly. An agent can tell what it does 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 Guidelines4/5

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

"Use to verify that outbound email signatures are cryptographically sound" gives a clear use case, and "Part of the scan_domain audit" situates it relative to a sibling. However, it names no exclusions or explicit alternative (e.g., when to prefer check_dmarc or check_bimi instead), so it stops short of full when-to-use guidance.

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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