Blackwood State

Email address check

blackwood_email_check

Read-onlyIdempotent

Use when you need email validation or to verify email addresses (domain, MX records) before sending, signup or lead scoring. Do not use for confirming that the mailbox itself exists (no SMTP probe is done) or sending email. Returns JSON with an email address check: syntax, domain and 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.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`email`	Yes	Email address to check, e.g. jane@example.com
`response_format`	No	concise (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

TableJSON Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedOct 17, 2026

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"
+  }
+]

AddedOct 17, 2026

TDQS

A4.6/5.0

Behavior5/5

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

Beyond annotations (readOnly/idempotent/non-destructive/openWorld), it discloses the absence of an SMTP probe, the per-call price (0.005 USDC), and p95 latency (800 ms) – none of which are in the annotations or schema. These are material traits for cost- and time-aware agents.

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?

It is front-loaded with the usage trigger and packs when/when-not/cost/latency into a compact block, ending with a category tag. Dense but each clause carries information; slightly overloaded into few sentences.

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, yet the description still summarizes the verdict fields, and it covers prerequisites, exclusions, cost and latency. Nothing an agent needs 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.

Parameters3/5

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

Schema coverage is 100%, with both 'email' and the 'response_format' enum fully described in the schema, so the description adds no parameter semantics beyond structured data. Baseline 3 applies when the schema does the heavy lifting.

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 states a specific verb+resource ('email validation / verify email addresses') and scopes exactly what is checked (domain, MX records). It clearly differentiates from the sibling blackwood_email_batch and from mailbox-verification semantics by naming what it does not do.

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?

It gives explicit positive triggers ('before sending, signup or lead scoring') and explicit exclusions ('Do not use for confirming that the mailbox itself exists... or sending email'). An agent can route to or away from this tool without inspecting siblings.

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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