BlackVeil DNS & Email Security Scanner

check_srv

Read-onlyIdempotent

Map a domain's DNS-visible service footprint by probing 19 common SRV record prefixes (email, calendar, messaging, directory, web) in parallel. Returns discovered services and flags insecure service advertisements — e.g. plaintext IMAP/POP3/LDAP without an encrypted variant. A domain with no matches among the probed prefixes is not proof the domain has no services at all. Use when asked to map DNS-visible services or flag insecure service advertisements.

Input 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

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 25, 2026
- addedInput schema / additionalProperties
```
Added value: +false
```
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

A4.1/5.0

Behavior4/5

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

Annotations already cover read-only, idempotent, non-destructive, open-world behavior. The description adds value beyond them: parallel probing of 19 prefixes, the returned artifacts (discovered services + insecure-advertisement flags), and a genuine caveat that absence of matches is not proof of no services. It omits freshness/caching semantics that would fully close the loop.

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?

Three well-scoped sentences: behavior, return/caveat, and usage trigger, all front-loaded and earning their place. Slightly dense but no filler.

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, full schema coverage, and annotations covering safety, the definition gives an agent enough to call correctly, plus an important false-negative caveat. Minor gaps like caching behavior don't undermine correct invocation.

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 each of the three parameters is already documented in the schema. The description adds no syntax or format detail for domain/format/force_refresh, so the 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 ('Map') and resource ('DNS-visible service footprint'), plus the exact mechanism (probing 19 common SRV record prefixes across email, calendar, messaging, directory, web). This clearly differentiates it from DNS siblings like check_svcb_https and check_mx, which share the SRV/record space.

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?

Ends with an explicit usage trigger ('Use when asked to map DNS-visible services or flag insecure service advertisements'). However, it never names or routes to an alternative sibling when that condition isn't met, so no exclusions are given.

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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