domain-security-mcp-server

SPF Record Check

spf_check

Read-onlyIdempotent

Check a domain's SPF record to detect missing or multiple records, verify the 'all' qualifier, and count DNS lookups against the RFC 7208 limit of 10.

Instructions

Fetch and analyse a domain's SPF record. Detects: missing/multiple records, the trailing 'all' qualifier (+all/?all/~all/-all), and counts DNS-querying terms recursively against the RFC 7208 limit of 10.

Args:

domain (string): the domain to check.
response_format ('markdown' | 'json'): output format (default 'markdown').

Returns: { found, record, multiple_records, all_qualifier, lookup_count, exceeds_lookup_limit, findings[] }.

Example: "Does sendgrid.net's SPF exceed the 10-lookup limit?" -> spf_check(domain="sendgrid.net").

Input Schema

TableJSON Schema

Name	Required	Description	Default
`domain`	Yes	Domain to check, e.g. 'example.com'.
`response_format`	No	Output format: 'markdown' for a human-readable summary (default) or 'json' for the full structured payload.	markdown

Output Schema

TableJSON Schema

Name	Required	Description	Default
`found`	Yes
`domain`	Yes
`record`	No
`findings`	Yes
`lookup_count`	Yes
`all_qualifier`	No
`multiple_records`	Yes
`exceeds_lookup_limit`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed4 schema fields changedv1.2.1Sep 14, 2026

changedInput schema / $schema

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

removedInput schema / additionalProperties
```
Removed value: -false
```
addedInput schema / properties / domain / maxLength
```
Added value: +253
```

changedOutput schema / $schema

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

First observedv1.0.0Jun 8, 2026

TDQS

A4.5/5.0

Behavior5/5

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

Annotations already declare the tool read-only and idempotent, and the description adds meaningful behavioral detail beyond that: it recursively counts DNS-querying terms against the RFC 7208 limit, detects qualifier variants, and exposes a structured return payload. This gives the agent a clear model of what the tool computes.

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?

The description is compact and well-organized: a front-loaded summary, a small Args block, a Returns line, and a single illustrative example. Every section adds value and there is no filler.

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?

Given the tool's complexity, the description covers the analysis logic, the return shape, the parameters, and a usage example. With read-only/idempotent annotations and an output schema already present, nothing essential is missing for 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 the schema already documents both parameters and the response_format default. The description repeats these details and adds an example, but provides no substantive semantic information beyond what the schema already offers; 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?

The description opens with a specific verb and resource: 'Fetch and analyse a domain's SPF record.' It then enumerates the concrete detections (missing/multiple records, trailing 'all' qualifier, RFC 7208 lookup limit), which clearly distinguishes it from sibling tools like dmarc_check and dkim_check.

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?

The description gives clear context for when the tool is appropriate and includes a concrete example question ('Does sendgrid.net's SPF exceed the 10-lookup limit?'). It does not explicitly name alternatives or exclusion conditions, so it stops short of a 5.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.