# SPF checker

- Human page: https://happytails.ai/en/email-tools/spf-checker/
- Markdown: https://happytails.ai/en/email-tools/spf-checker.md
- Structured JSON: https://happytails.ai/agents/en/email-tools/spf-checker/index.json
- Visibility: public

## Tool capabilities

| Property | Value |
| --- | --- |
| Tool ID | `spf-checker` |
| Category | email-tools |
| Implementation | Registered implementation. Registration alone is not a production-quality guarantee. |
| Browser execution | Use the visible action or interactive controls. |
| Browser processing | Server required |
| HTTP API | /api/v1/tools/spf-checker/run |
| Browser-agent interface | run_current_tool |

### Implementation notes

Uses the local diagnostic server to contact the supplied public host or DNS/RDAP provider. Only public internet addresses are permitted; requests time out and redirects are bounded.

### Inputs and settings

Text input: Domain name.

Example or placeholder shown in the interface (not a validated fixture):

```text
happytails.ai
```

Enter one domain name without https://, a path or a port.

No additional settings are declared for this tool.

### HTTP contract

API calls process supplied data on the server. The website origin is `https://happytails.ai`. Server API hosting is not connected on the public website yet. Use your local server origin to test these requests.

```http
POST https://happytails.ai/api/v1/tools/spf-checker/run
Content-Type: application/json
```

[Detailed operation reference](https://happytails.ai/en/api/tools/spf-checker.md) · [Shared API guide](https://happytails.ai/en/api.md)

#### Limits

| Limit | Value |
| --- | --- |
| request_bytes | 8388608 |
| input_characters | 1000000 |
| files_bytes | 5242880 |
| max_files | 0 |
| timeout_seconds | Operation-specific network bounds |

#### Complete input schema

```json
{
  "type": "object",
  "additionalProperties": false,
  "properties": {
    "input": {
      "type": "string",
      "maxLength": 1000000,
      "default": "",
      "description": "Plain text input. File tools use files instead unless otherwise documented."
    },
    "options": {
      "type": "object",
      "additionalProperties": false,
      "properties": {}
    }
  }
}
```

#### Complete output schema

```json
{
  "type": "object",
  "required": [
    "tool",
    "result"
  ],
  "properties": {
    "tool": {
      "type": "string"
    },
    "result": {
      "type": "object",
      "required": [
        "text",
        "files"
      ],
      "properties": {
        "text": {
          "type": [
            "string",
            "null"
          ]
        },
        "data": {
          "description": "Parsed JSON when the textual result is JSON."
        },
        "name": {
          "type": "string"
        },
        "mime": {
          "type": "string"
        },
        "files": {
          "type": "array",
          "items": {
            "type": "object",
            "required": [
              "name",
              "mime",
              "bytes",
              "base64"
            ],
            "properties": {
              "name": {
                "type": "string"
              },
              "mime": {
                "type": "string"
              },
              "bytes": {
                "type": "integer"
              },
              "base64": {
                "type": "string",
                "contentEncoding": "base64"
              }
            }
          }
        }
      }
    }
  }
}
```

#### Error and retry handling

Failures return a non-200 status and `error.code` plus `error.message`. Correct invalid input before retrying; retry server-busy responses with bounded backoff. Returned files contain Base64 data, not persistent download URLs. Decode and inspect the output before treating conversion as successful. See the shared API guide for the complete status and timeout rules.

### Browser-agent workflow

1. Open the human page in a browser that supports WebMCP.
2. Discover the interface exposed by that page; use its actual schema.
3. Select files on the page first when the tool requires files.
4. Call `run_current_tool` with valid input and settings.
5. Inspect the returned result or error and the displayed output. Retrieve files from the displayed download links.

Calls do not automatically copy or download results. Browser permissions still apply. Interface availability alone is not proof of successful execution.

### Planning specification

DNS lookups, include-chain limits and findings; never infer delivery guarantee.

This describes intended requirements. Use the implementation notes, interface schema and observed output to determine current support.

### Complete machine-readable capability record

```json
{
  "id": "spf-checker",
  "category": "email-tools",
  "built": true,
  "requirements": "DNS lookups, include-chain limits and findings; never infer delivery guarantee.",
  "implementation": {
    "fields": [],
    "processing": "Server required",
    "note": "Uses the local diagnostic server to contact the supplied public host or DNS/RDAP provider. Only public internet addresses are permitted; requests time out and redirects are bounded.",
    "experience": {
      "automatic": false,
      "single": true,
      "label": "Domain name",
      "placeholder": "happytails.ai",
      "help": "Enter one domain name without https://, a path or a port.",
      "action": "Check domain"
    },
    "mode": "explicit",
    "interactive": false
  },
  "execution": "POST /api/v1/tools/spf-checker/run",
  "api": {
    "id": "spf-checker",
    "name": "SPF checker",
    "category": "email-tools",
    "description": "DNS lookups, include-chain limits and findings.",
    "notes": "Uses the local diagnostic server to contact the supplied public host or DNS/RDAP provider. Only public internet addresses are permitted; requests time out and redirects are bounded.",
    "human_path": "/en/email-tools/spf-checker/",
    "method": "POST",
    "endpoint": "/api/v1/tools/spf-checker/run",
    "schema_url": "/api/v1/tools/spf-checker",
    "input_schema": {
      "type": "object",
      "additionalProperties": false,
      "properties": {
        "input": {
          "type": "string",
          "maxLength": 1000000,
          "default": "",
          "description": "Plain text input. File tools use files instead unless otherwise documented."
        },
        "options": {
          "type": "object",
          "additionalProperties": false,
          "properties": {}
        }
      }
    },
    "output_schema": {
      "type": "object",
      "required": [
        "tool",
        "result"
      ],
      "properties": {
        "tool": {
          "type": "string"
        },
        "result": {
          "type": "object",
          "required": [
            "text",
            "files"
          ],
          "properties": {
            "text": {
              "type": [
                "string",
                "null"
              ]
            },
            "data": {
              "description": "Parsed JSON when the textual result is JSON."
            },
            "name": {
              "type": "string"
            },
            "mime": {
              "type": "string"
            },
            "files": {
              "type": "array",
              "items": {
                "type": "object",
                "required": [
                  "name",
                  "mime",
                  "bytes",
                  "base64"
                ],
                "properties": {
                  "name": {
                    "type": "string"
                  },
                  "mime": {
                    "type": "string"
                  },
                  "bytes": {
                    "type": "integer"
                  },
                  "base64": {
                    "type": "string",
                    "contentEncoding": "base64"
                  }
                }
              }
            }
          }
        }
      }
    },
    "processing": "Server; contacts public network services",
    "limits": {
      "request_bytes": 8388608,
      "input_characters": 1000000,
      "files_bytes": 5242880,
      "max_files": 0,
      "timeout_seconds": null
    }
  },
  "agent_processing": "Server; contacts public network services",
  "browser_agent": {
    "supported": true,
    "name": "run_current_tool",
    "discovery": "WebMCP on the human page in a supporting browser",
    "verification": "See audit/API-AUDIT.md; availability is not verification"
  }
}
```

## Page guide

DNS lookups, include-chain limits and findings.

## How to use SPF checker

1. Enter a domain name in the input field.
2. Review the settings, then choose Check domain.
3. Review the result, then use Copy result or a download link when available.

## Working with spf checker

Email tools can inspect addresses, message headers, templates and domain configuration. These tasks answer different questions: a syntactically valid address is not the same as a mailbox that exists, and a configured domain is not a guarantee of inbox placement.

## Common questions

### Does address validation prove a mailbox exists?

Syntax checks can catch formatting mistakes but cannot prove that a person receives mail at an address. Server-side checks can also be inconclusive.

### Do authentication records guarantee inbox delivery?

No. Authentication is one signal among several. Sending behavior, recipient engagement and filtering rules also affect what happens to a message.

## Useful next steps

- [DKIM checker](https://happytails.ai/en/email-tools/dkim-checker/): Domain plus selector lookup. ([Markdown](https://happytails.ai/en/email-tools/dkim-checker.md))

- [DMARC checker](https://happytails.ai/en/email-tools/dmarc-checker/): Parse policy, reporting addresses and inheritance. ([Markdown](https://happytails.ai/en/email-tools/dmarc-checker.md))

- [DNS lookup](https://happytails.ai/en/network-tools/dns-lookup/): A AAAA MX TXT CNAME NS SOA records with resolver and time. ([Markdown](https://happytails.ai/en/network-tools/dns-lookup.md))