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Blackwood State

by io.github.Blackwood-State
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Email validation

blackwood_email_check
Read-onlyIdempotent

Use when you need email validation, to verify email addresses or validate email syntax and MX records before sending or signup. Do not use for confirming that the mailbox itself exists (no SMTP probe is done) or sending email. Returns JSON with email verification of one address: syntax, domain MX records, disposable, free and role-account flags, SPF and DMARC, and a verdict on whether the domain can receive mail for 0.005 USDC per call. Typical response time 800 ms (p95). Category: Data.

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": {
      "email": "<email>"
    },
    "name": "blackwood_email_check"
  }
}

Input Schema

NameRequiredDescriptionDefault
emailYesEmail address to check, e.g. jane@example.com
response_formatNoconcise (the default when omitted) keeps the JSON short: long fields such as base64 images or audio come back as separate image/audio content blocks and other long strings are cut with a marker; detailed returns the full JSON

Output Schema

NameRequiredDescriptionDefault

No arguments

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changed
    • changedOutput schema / anyOf
      Previous value: -[
-  {
-    "additionalProperties": false,
-    "properties": {
-      "acceptsMail": {
-        "type": "boolean"
-      },
-      "disposable": {
-        "type": "boolean"
-      },
-      "dmarc": {
-        "type": [
-          "string",
-          "null"
-        ]
-      },
-      "dmarcPolicy": {
-        "type": [
-          "string",
-          "null"
-        ]
-      },
-      "domain": {
-        "type": [
-          "string",
-          "null"
-        ]
-      },
-      "domainExists": {
-        "type": [
-          "boolean",
-          "null"
-        ]
-      },
-      "email": {
-        "type": "string"
-      },
-      "freeProvider": {
-        "type": "boolean"
-      },
-      "mx": {
-        "items": {
-          "additionalProperties": false,
-          "properties": {
-            "host": {
-              "type": "string"
-            },
-            "priority": {
-              "type": "number"
-            }
-          },
-          "required": [
-            "priority",
-            "host"
-          ],
-          "type": "object"
-        },
-        "type": "array"
-      },
-      "normalized": {
-        "type": [
-          "string",
-          "null"
-        ]
-      },
-      "reasons": {
-        "items": {
-          "type": "string"
-        },
-        "type": "array"
-      },
-      "roleAccount": {
-        "type": "boolean"
-      },
-      "smtpChecked": {
-        "type": "boolean"
-      },
-      "spf": {
-        "type": [
-          "string",
-          "null"
-        ]
-      },
-      "syntaxValid": {
-        "type": "boolean"
-      },
-      "verdict": {
-        "enum": [
-          "deliverable_domain",
-          "risky",
-          "undeliverable",
-          "invalid"
-        ],
-        "type": "string"
-      }
-    },
-    "required": [
-      "email",
-      "normalized",
-      "syntaxValid",
-      "domain",
-      "disposable",
-      "freeProvider",
-      "roleAccount",
-      "domainExists",
-      "mx",
-      "acceptsMail",
-      "spf",
-      "dmarc",
-      "dmarcPolicy",
-      "verdict",
-      "reasons",
-      "smtpChecked"
-    ],
-    "type": "object"
-  },
-  {
-    "description": "x402 PaymentRequired (returned with isError when payment is needed)",
-    "properties": {
-      "accepts": {
-        "items": {
-          "type": "object"
-        },
-        "type": "array"
-      },
-      "error": {
-        "type": "string"
-      },
-      "extensions": {
-        "type": "object"
-      },
-      "resource": {
-        "type": "object"
-      },
-      "x402Version": {
-        "type": "integer"
-      }
-    },
-    "required": [
-      "x402Version",
-      "accepts"
-    ],
-    "type": "object"
-  }
-]New value: +[
+  {
+    "additionalProperties": false,
+    "properties": {
+      "acceptsMail": {
+        "type": "boolean"
+      },
+      "disposable": {
+        "type": "boolean"
+      },
+      "dmarc": {
+        "type": [
+          "string",
+          "null"
+        ]
+      },
+      "dmarcPolicy": {
+        "type": [
+          "string",
+          "null"
+        ]
+      },
+      "domain": {
+        "type": [
+          "string",
+          "null"
+        ]
+      },
+      "domainExists": {
+        "type": [
+          "boolean",
+          "null"
+        ]
+      },
+      "email": {
+        "type": "string"
+      },
+      "freeProvider": {
+        "type": "boolean"
+      },
+      "mx": {
+        "items": {
+          "additionalProperties": false,
+          "properties": {
+            "host": {
+              "type": "string"
+            },
+            "priority": {
+              "type": "number"
+            }
+          },
+          "required": [
+            "priority",
+            "host"
+          ],
+          "type": "object"
+        },
+        "type": "array"
+      },
+      "next": {
+        "additionalProperties": false,
+        "description": "Suggested next paid call in the same family (call it in a loop when the task continues)",
+        "properties": {
+          "method": {
+            "enum": [
+              "GET",
+              "POST"
+            ],
+            "type": "string"
+          },
+          "sample": {
+            "description": "Free fixed sample of the whole family",
+            "type": "string"
+          },
+          "service": {
+            "description": "Service id of the suggested next paid call",
+            "type": "string"
+          },
+          "tool": {
+            "description": "MCP tool name of the same call",
+            "type": "string"
+          },
+          "url": {
+            "description": "Paid route of the next call",
+            "type": "string"
+          },
+          "useWhen": {
+            "description": "When the next call is the right one",
+            "type": "string"
+          }
+        },
+        "required": [
+          "service",
+          "tool",
+          "method",
+          "url",
+          "useWhen",
+          "sample"
+        ],
+        "type": "object"
+      },
+      "normalized": {
+        "type": [
+          "string",
+          "null"
+        ]
+      },
+      "reasons": {
+        "items": {
+          "type": "string"
+        },
+        "type": "array"
+      },
+      "roleAccount": {
+        "type": "boolean"
+      },
+      "smtpChecked": {
+        "type": "boolean"
+      },
+      "spf": {
+        "type": [
+          "string",
+          "null"
+        ]
+      },
+      "syntaxValid": {
+        "type": "boolean"
+      },
+      "verdict": {
+        "enum": [
+          "deliverable_domain",
+          "risky",
+          "undeliverable",
+          "invalid"
+        ],
+        "type": "string"
+      }
+    },
+    "required": [
+      "email",
+      "normalized",
+      "syntaxValid",
+      "domain",
+      "disposable",
+      "freeProvider",
+      "roleAccount",
+      "domainExists",
+      "mx",
+      "acceptsMail",
+      "spf",
+      "dmarc",
+      "dmarcPolicy",
+      "verdict",
+      "reasons",
+      "smtpChecked"
+    ],
+    "type": "object"
+  },
+  {
+    "description": "x402 PaymentRequired (returned with isError when payment is needed)",
+    "properties": {
+      "accepts": {
+        "items": {
+          "type": "object"
+        },
+        "type": "array"
+      },
+      "error": {
+        "type": "string"
+      },
+      "extensions": {
+        "type": "object"
+      },
+      "resource": {
+        "type": "object"
+      },
+      "x402Version": {
+        "type": "integer"
+      }
+    },
+    "required": [
+      "x402Version",
+      "accepts"
+    ],
+    "type": "object"
+  }
+]
  2. Added

TDQS

A4.5/5.0
Behavior4/5

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

Annotations already declare readOnly/idempotent/non-destructive, but the description adds genuinely non-structured behavior: 0.005 USDC per call pricing, 800 ms p95 latency, and the no-SMTP-probe limitation. The enumeration of return fields overlaps what the output schema already provides, so this is strong but not maximally additive.

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 dense paragraph, front-loaded with the usage cue, then scope exclusions, then returns and cost. No sentence is filler; cost and latency earn their place.

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 paid, network-bound validation tool with full annotations, complete schema, and an output schema, the description covers trigger, exclusions, return shape, and cost/latency. Nothing required for correct invocation is missing.

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 baseline is 3. The description says nothing about the 'email' or 'response_format' parameters that isn't already in the schema, so it neither compensates nor adds value here.

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 and resource ('email validation', 'verify email addresses or validate email syntax and MX records') and sharply bounds scope by contrasting with sibling-adjacent functions (no mailbox existence check, no sending). An agent can tell this single-address validator apart from batch or send-email tools without opening a schema.

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?

Gives explicit trigger context ('before sending or signup') and two explicit exclusions ('Do not use for confirming that the mailbox itself exists... or sending email'). This is the when/when-not pattern done properly.

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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