scan.mx Email Diagnostics

Check SPF

check_spf

Read-only

Check the domain SPF policy: presence, syntax, the all qualifier, and the 10-lookup limit.

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	Default
`domain`	Yes	The domain to check, e.g. example.com. No scheme or path.

Output Schema

Name	Required	Description	Default
`grade`	No
`score`	No
`checks`	No
`domain`	Yes
`provider`	No
`sections`	No
`selector`	No
`permalink`	No
`smtp_note`	No
`created_at`	No
`expires_at`	No
`updated_at`	No
`smtp_status`	No
`poll_after_seconds`	No

Schema Changelog

Changes observed during successful MCP inspections.

First observedJul 9, 2026

TDQS

A4/5.0

Behavior4/5

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

Annotations already indicate read-only and open-world hints. The description adds behavioral specifics by naming the four checks performed (presence, syntax, all qualifier, 10-lookup limit), which is useful context beyond the annotations.

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?

Single sentence with no redundancy. Front-loads the main action and lists specific checks efficiently. Every word earns its place.

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, the description need not detail return values. It covers the core functionality (SPF policy checks) but could mention behavior on invalid domains or vague outcomes.

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 coverage is 100% with a clear parameter description. The tool description does not add additional parameter-level meaning beyond what the schema already provides, so 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 clearly states it checks the domain SPF policy, listing specific aspects (presence, syntax, all qualifier, 10-lookup limit). This distinguishes it from sibling tools like check_dkim or check_dmarc which target different DNS records.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

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

No explicit guidance on when to use this tool versus alternatives. The usage is implied by the tool name and description but lacks clear directives like 'use this when checking SPF validity' or mention of alternatives.

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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