BlackVeil DNS & Email Security Scanner

check_spf

Read-onlyIdempotent

Look up and validate the SPF record for a domain. Lists all IP addresses and third-party senders authorised to send email on behalf of the domain, flags syntax errors, and shows the trust surface (which mail servers are whitelisted). Use when you need to know who is permitted to send email as a domain. Part of the scan_domain audit.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "domain": "<domain>"
    },
    "name": "check_spf"
  }
}

Input Schema

Name	Required	Description
`domain`	Yes	Domain, e.g. example.com
`format`	No	Output verbosity.
`force_refresh`	No	Bypass the cache.

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.

Changed3 schema fields changedNov 12, 2026

changedInput schema / properties / domain / description

Previous value: -"Domain to check (e.g., example.com)"New value: +"Domain, e.g. example.com"

changedInput schema / properties / force_refresh / description

Previous value: -"Bypass cache and run a fresh check. Useful after DNS changes."New value: +"Bypass the cache."

changedInput schema / properties / format / description

Previous value: -"Output verbosity. Auto-detected if omitted."New value: +"Output verbosity."

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

A3.9/5.0

Behavior4/5

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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so safety is covered; the description adds real substance on top by disclosing the response contents (IP list, third-party senders, syntax-error flags, trust surface) and the fact this is an external lookup. It omits any mention of the cache that force_refresh exists to bypass, which is the one behavioural gap.

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 tight sentences, front-loaded with the operation and then the value it produces, with no filler. The trailing 'Part of the scan_domain audit' is short but slightly orphaned from the when-to-use sentence it would have strengthened if merged.

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 do not need spelling out, and annotations carry the safety profile; the description still covers purpose, trigger and output shape. The remaining shortfall is that a read-only network tool with a cache parameter says nothing about caching or lookup cost.

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 defines domain, format and force_refresh with its enum and cache semantics. The description adds nothing about how those parameters alter the result, so the baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

Opens with a specific verb+resource ('Look up and validate the SPF record for a domain') and enumerates the concrete outputs (authorised IPs, third-party senders, syntax errors, trust surface), so the agent knows exactly what it gets. It also positions itself inside a 'scan_domain audit', which hints at the broader sibling, but it never contrasts with resolve_spf_chain, leaving one obvious neighbour undistinguished.

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 when you need to know who is permitted to send email as a domain" gives a clear triggering condition rather than a bare restatement. No exclusions are stated, so an agent cannot tell from the description alone when to prefer resolve_spf_chain or the full scan_domain over this check.

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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