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DMARC check

dmarc_check
Read-only

Fetches a domain's DMARC record from _dmarc. and evaluates it: raw record, parsed tags, policy and subdomain policy, percentage, and warnings for records that parse but offer no protection (p=none, missing rua). Reports the published policy, not whether real mail passes it; spf_check and dkim_check cover the mechanisms it aligns against. Anonymous, rate-limited per IP.

Input Schema

NameRequiredDescriptionDefault
domainYesDomain name, e.g. deinkunde.com

Output Schema

NameRequiredDescriptionDefault
okNo
pctNo
tagsNo
errorNo
foundNo
domainNo
policyNo
recordNo
warningsNo
subPolicyNo

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed17 schema fields changed
    • removedOutput schema / properties / domain / anyOf
      Removed value: -[
      -  {
      -    "type": "string"
      -  },
      -  {
      -    "type": "null"
      -  }
      -]
    • addedOutput schema / properties / domain / type
      Added value: +[
      +  "string",
      +  "null"
      +]
    • removedOutput schema / properties / error / anyOf
      Removed value: -[
      -  {
      -    "type": "string"
      -  },
      -  {
      -    "type": "null"
      -  }
      -]
    • addedOutput schema / properties / error / type
      Added value: +[
      +  "string",
      +  "null"
      +]
    • removedOutput schema / properties / found / anyOf
      Removed value: -[
      -  {
      -    "type": "boolean"
      -  },
      -  {
      -    "type": "null"
      -  }
      -]
    • addedOutput schema / properties / found / type
      Added value: +[
      +  "boolean",
      +  "null"
      +]
    • removedOutput schema / properties / ok / anyOf
      Removed value: -[
      -  {
      -    "type": "boolean"
      -  },
      -  {
      -    "type": "null"
      -  }
      -]
    • addedOutput schema / properties / ok / type
      Added value: +[
      +  "boolean",
      +  "null"
      +]
    • removedOutput schema / properties / pct / anyOf
      Removed value: -[
      -  {
      -    "type": "number"
      -  },
      -  {
      -    "type": "null"
      -  }
      -]
    • addedOutput schema / properties / pct / type
      Added value: +[
      +  "number",
      +  "null"
      +]
    • removedOutput schema / properties / policy / anyOf
      Removed value: -[
      -  {
      -    "type": "string"
      -  },
      -  {
      -    "type": "null"
      -  }
      -]
    • addedOutput schema / properties / policy / type
      Added value: +[
      +  "string",
      +  "null"
      +]
    • removedOutput schema / properties / record / anyOf
      Removed value: -[
      -  {
      -    "type": "string"
      -  },
      -  {
      -    "type": "null"
      -  }
      -]
    • addedOutput schema / properties / record / type
      Added value: +[
      +  "string",
      +  "null"
      +]
    • removedOutput schema / properties / subPolicy / anyOf
      Removed value: -[
      -  {
      -    "type": "string"
      -  },
      -  {
      -    "type": "null"
      -  }
      -]
    • addedOutput schema / properties / subPolicy / type
      Added value: +[
      +  "string",
      +  "null"
      +]
    • changedOutput schema / properties / tags / anyOf
      Previous value: -[
      -  {
      -    "items": {
      -      "additionalProperties": {},
      -      "properties": {
      -        "tag": {
      -          "anyOf": [
      -            {
      -              "type": "string"
      -            },
      -            {
      -              "type": "null"
      -            }
      -          ]
      -        },
      -        "value": {
      -          "anyOf": [
      -            {
      -              "type": "string"
      -            },
      -            {
      -              "type": "null"
      -            }
      -          ]
      -        }
      -      },
      -      "type": "object"
      -    },
      -    "type": "array"
      -  },
      -  {
      -    "type": "null"
      -  }
      -]New value: +[
      +  {
      +    "items": {
      +      "additionalProperties": {},
      +      "properties": {
      +        "tag": {
      +          "type": [
      +            "string",
      +            "null"
      +          ]
      +        },
      +        "value": {
      +          "type": [
      +            "string",
      +            "null"
      +          ]
      +        }
      +      },
      +      "type": "object"
      +    },
      +    "type": "array"
      +  },
      +  {
      +    "type": "null"
      +  }
      +]
  2. Changed1 schema field changed
    • changedOutput schema / (root)
      Previous value: -nullNew value: +{
      +  "$schema": "http://json-schema.org/draft-07/schema#",
      +  "additionalProperties": {},
      +  "properties": {
      +    "domain": {
      +      "anyOf": [
      +        {
      +          "type": "string"
      +        },
      +        {
      +          "type": "null"
      +        }
      +      ]
      +    },
      +    "error": {
      +      "anyOf": [
      +        {
      +          "type": "string"
      +        },
      +        {
      +          "type": "null"
      +        }
      +      ]
      +    },
      +    "found": {
      +      "anyOf": [
      +        {
      +          "type": "boolean"
      +        },
      +        {
      +          "type": "null"
      +        }
      +      ]
      +    },
      +    "ok": {
      +      "anyOf": [
      +        {
      +          "type": "boolean"
      +        },
      +        {
      +          "type": "null"
      +        }
      +      ]
      +    },
      +    "pct": {
      +      "anyOf": [
      +        {
      +          "type": "number"
      +        },
      +        {
      +          "type": "null"
      +        }
      +      ]
      +    },
      +    "policy": {
      +      "anyOf": [
      +        {
      +          "type": "string"
      +        },
      +        {
      +          "type": "null"
      +        }
      +      ]
      +    },
      +    "record": {
      +      "anyOf": [
      +        {
      +          "type": "string"
      +        },
      +        {
      +          "type": "null"
      +        }
      +      ]
      +    },
      +    "subPolicy": {
      +      "anyOf": [
      +        {
      +          "type": "string"
      +        },
      +        {
      +          "type": "null"
      +        }
      +      ]
      +    },
      +    "tags": {
      +      "anyOf": [
      +        {
      +          "items": {
      +            "additionalProperties": {},
      +            "properties": {
      +              "tag": {
      +                "anyOf": [
      +                  {
      +                    "type": "string"
      +                  },
      +                  {
      +                    "type": "null"
      +                  }
      +                ]
      +              },
      +              "value": {
      +                "anyOf": [
      +                  {
      +                    "type": "string"
      +                  },
      +                  {
      +                    "type": "null"
      +                  }
      +                ]
      +              }
      +            },
      +            "type": "object"
      +          },
      +          "type": "array"
      +        },
      +        {
      +          "type": "null"
      +        }
      +      ]
      +    },
      +    "warnings": {
      +      "anyOf": [
      +        {
      +          "items": {
      +            "type": "string"
      +          },
      +          "type": "array"
      +        },
      +        {
      +          "type": "null"
      +        }
      +      ]
      +    }
      +  },
      +  "type": "object"
      +}
  3. First observed

TDQS

A4.7/5.0
Behavior4/5

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

Adds real behavioral context beyond the readOnlyHint/openWorldHint annotations: anonymous access, per-IP rate limiting, the _dmarc.<domain> lookup location, and the warning heuristics for p=none/missing rua. It doesn't detail rate-limit values or timeout/error behavior, keeping it just short of a 5.

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?

Two dense sentences, front-loaded with the fetch-and-evaluate action, with scope caveats and the sibling pointer placed after. 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?

An output schema exists, so return values need not be explained; the description nonetheless covers scope, warning behavior, access model, and alternatives. Nothing needed to call it correctly is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the baseline is 3, but the description adds meaning by revealing how the single parameter is used: it is prepended with _dmarc. to form the lookup name. That is genuine semantic value beyond the schema's 'domain name' hint.

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+resource and enumerates exactly what it evaluates (raw record, parsed tags, policy, subdomain policy, percentage, warnings). It also distinguishes itself from siblings by noting spf_check and dkim_check cover the alignment mechanisms instead.

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

Usage Guidelines5/5

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

Explicitly scopes the tool: it reports the published policy, not whether real mail passes it, and names spf_check/dkim_check as the alternatives for mechanism-level checks. An agent can route correctly with no inference.

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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