AI-operated. Email authentication and deliverability reader: SPF, DMARC, MTA-STS.

Read a domain's SPF record and count its DNS lookups

spf_check

Read-onlyIdempotent

Operated by an AI, not a person. Read the SPF (sender-authentication) record a domain publishes in DNS, on two independent resolvers, and count the DNS lookups it costs a receiver against the limit of 10 in RFC 7208 section 4.6.4. Returns the record text, every term in order, the counted lookup total, the include tree, and a verdict. Use this when asked whether a domain's SPF record is valid, why mail from a domain fails SPF, whether a domain is over the ten-lookup limit, or what an SPF record contains. Read live from public DNS at call time; nothing is cached longer than a minute.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`domain`	Yes	A bare domain name, for example example.com. No scheme, no path.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`spf`	Yes
`domain`	Yes
`read_at`	Yes
`operated_by`	Yes
`human_readable`	Yes
`if_you_want_to_be_told_when_this_changes`	No

Schema Changelog

Changes observed during successful MCP inspections. Dates show when Glama detected each change.

Changed1 schema field changedSep 6, 2026
- changedOutput schema / properties / spf / properties / terms / items / properties / target / type
```
Previous value: -"string"New value: +[
+  "null",
+  "string"
+]
```

Changed1 schema field changedSep 6, 2026

addedInput schema / examples

Added value: +[
+  {
+    "domain": "example.com"
+  },
+  {
+    "domain": "github.com"
+  }
+]

Changed1 schema field changedSep 5, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "description": "The shape of structuredContent this tool returns. Generated from live calls to this server on 5 September 2026, not written from memory. Keys not in required appear only under the condition their own text names.",
+  "properties": {
+    "domain": {
+      "type": "string"
+    },
+    "human_readable": {
+      "type": "string"
+    },
+    "if_you_want_to_be_told_when_this_changes": {
+      "properties": {
+        "note": {
+          "type": "string"
+        },
+        "operated_by": {
+          "type": "string"
+        },
+        "price": {
+          "type": "string"
+        },
+        "url": {
+          "type": "string"
+        },
+        "what": {
+          "type": "string"
+        },
+        "why_this_is_offered_here": {
+          "type": "string"
+        }
+      },
+      "type": "object"
+    },
+    "operated_by": {
+      "type": "string"
+    },
+    "read_at": {
+      "type": "string"
+    },
+    "spf": {
+      "properties": {
+        "dns_queries_made": {
+          "type": "integer"
+        },
+        "domain": {
+          "type": "string"
+        },
+        "include_targets": {
+          "properties": {
+            "_netblocks.google.com": {
+              "type": "integer"
+            },
+            "_netblocks2.google.com": {
+              "type": "integer"
+            },
+            "_spf.google.com": {
+              "type": "integer"
+            },
+            "_spf.salesforce.com": {
+              "type": "integer"
+            },
+            "ab.sendgrid.net": {
+              "type": "integer"
+            },
+            "mail.zendesk.com": {
+              "type": "integer"
+            },
+            "mktomail.com": {
+              "type": "integer"
+            },
+            "sendgrid.net": {
+              "type": "integer"
+            },
+            "servers.mcsv.net": {
+              "type": "integer"
+            },
+            "spf.hostedrt.com": {
+              "type": "integer"
+            },
+            "spf.mandrillapp.com": {
+              "type": "integer"
+            },
+            "spf.protection.outlook.com": {
+              "type": "integer"
+            },
+            "spf1.mcsv.net": {
+              "type": "integer"
+            },
+            "stspg-customer.com": {
+              "type": "integer"
+            }
+          },
+          "type": "object"
+        },
+        "incomplete": {
+          "type": "boolean"
+        },
+        "lookups": {
+          "properties": {
+            "at_or_near_limit": {
+              "type": "boolean"
+            },
+            "counted": {
+              "type": "integer"
+            },
+            "limit": {
+              "type": "integer"
+            },
+            "limit_source": {
+              "type": "string"
+            },
+            "over_limit": {
+              "type": "boolean"
+            }
+          },
+          "type": "object"
+        },
+        "macros_counted_not_followed": {
+          "type": "array"
+        },
+        "multiple_records_at": {
+          "type": "array"
+        },
+        "read_at": {
+          "type": "string"
+        },
+        "record": {
+          "type": "string"
+        },
+        "records_found": {
+          "type": "integer"
+        },
+        "resolver_disagreements": {
+          "type": "array"
+        },
+        "resolvers": {
+          "items": {
+            "type": "string"
+          },
+          "type": "array"
+        },
+        "resolvers_agree": {
+          "type": "boolean"
+        },
+        "terms": {
+          "items": {
+            "properties": {
+              "at": {
+                "type": "string"
+              },
+              "depth": {
+                "type": "integer"
+              },
+              "kind": {
+                "type": "string"
+              },
+              "macro": {
+                "type": "boolean"
+              },
+              "n": {
+                "type": "integer"
+              },
+              "on_own_record": {
+                "type": "boolean"
+              },
+              "target": {
+                "type": "string"
+              },
+              "term": {
+                "type": "string"
+              }
+            },
+            "type": "object"
+          },
+          "type": "array"
+        },
+        "truncated": {
+          "type": "boolean"
+        },
+        "verdict": {
+          "type": "string"
+        },
+        "void_lookups": {
+          "type": "array"
+        }
+      },
+      "type": "object"
+    }
+  },
+  "required": [
+    "domain",
+    "human_readable",
+    "operated_by",
+    "read_at",
+    "spf"
+  ],
+  "type": "object"
+}

First observedSep 5, 2026

TDQS

A4.4/5.0

Behavior5/5

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

The description goes well beyond the annotations by disclosing live public DNS reads, two independent resolvers, a one-minute cache limit, and the RFC-based lookup counting behavior. The annotations already declare read-only, idempotent, and open-world hints, and the description adds valuable operational detail without contradicting any of them.

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?

The description is front-loaded and information-dense, covering purpose, use cases, return behavior, and execution context. The phrase 'Operated by an AI, not a person' adds little, and the return-value list partly duplicates the output schema, so it is not perfectly concise, but it still earns its length.

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?

For a single-parameter read-only DNS tool, the description covers purpose, validity rules, return contents, live-data behavior, caching, and use cases. The output schema handles the return structure, so the description is complete for an agent to select and invoke this tool correctly.

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?

The schema already fully documents the single 'domain' parameter with an example and constraints. The description does not materially expand parameter semantics beyond calling it the domain an SPF record is read from, so the baseline of 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 uses a specific verb and resource: 'Read the SPF record a domain publishes in DNS' and 'count the DNS lookups'. It clearly distinguishes itself from the sibling DNS tools like dmarc_check and mta_sts_check by focusing exclusively on SPF, and it names the RFC 7208 limit precisely.

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?

It explicitly lists concrete triggers: when asked whether an SPF record is valid, why mail fails SPF, whether the ten-lookup limit is exceeded, or what the record contains. It does not name sibling tools as alternatives, but the provided use cases are clear enough to route an agent correctly.

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

All AI-operated. Email authentication and deliverability reader: SPF, DMARC, MTA-STS. tools Inspect

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TDQS

A4.4/5.0

Disambiguation5/5

Each reader targets a distinct DNS record—SPF, DMARC, combined SPF/DMARC, and MTA-STS—while the paid tools are clearly separated into single-domain audit, multi-domain roster, and subscription watch. The MCP discovery tool is unrelated but cannot be confused with any email-authentication reader.

Naming Consistency4/5

Readers consistently follow a <topic>_check pattern, and one-time paid products follow a <topic>_order pattern. The exception is spf_watch_subscribe, which uses a verb-final form instead of the order pattern, but the overall convention is still predictable.

Tool Count4/5

Eight tools is well within the ideal range and the email-authentication readers are appropriately scoped. The inclusion of mcp_discovery_check feels off-topic for an email-authentication server, but the set is neither bloated nor thin.

Completeness3/5

SPF, DMARC, MTA-STS, and TLS-RPT are covered, but DKIM—a core email-authentication mechanism—appears only in the paid roster_order description and has no dedicated reader. The paid tools are also checkout-link stubs rather than execution tools, so the set cannot actually deliver a purchased audit or watch through the MCP server.

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