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DNSBL check

dnsbl_check
Read-only

Checks a public IP address against common DNS blocklists and returns, per list, whether it is listed, the list's reason code and delisting URL, plus totals and a clean flag. Takes an IP address, not a domain (mx_lookup or check_dns resolve one). Slow lists are skipped rather than awaited, so partial=true marks a provisional verdict. One call reflects only the current moment. Anonymous, with the strictest per-IP rate limit of the anonymous tools.

Input Schema

NameRequiredDescriptionDefault
ipYesPublic IPv4 or IPv6 address

Output Schema

NameRequiredDescriptionDefault
ipNo
okNo
cleanNo
totalNo
partialNo
resultsNo
listedCountNo
zonesQueriedNo

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed15 schema fields changed
    • removedOutput schema / properties / clean / anyOf
      Removed value: -[
      -  {
      -    "type": "boolean"
      -  },
      -  {
      -    "type": "null"
      -  }
      -]
    • addedOutput schema / properties / clean / type
      Added value: +[
      +  "boolean",
      +  "null"
      +]
    • removedOutput schema / properties / ip / anyOf
      Removed value: -[
      -  {
      -    "type": "string"
      -  },
      -  {
      -    "type": "null"
      -  }
      -]
    • addedOutput schema / properties / ip / type
      Added value: +[
      +  "string",
      +  "null"
      +]
    • removedOutput schema / properties / listedCount / anyOf
      Removed value: -[
      -  {
      -    "type": "number"
      -  },
      -  {
      -    "type": "null"
      -  }
      -]
    • addedOutput schema / properties / listedCount / type
      Added value: +[
      +  "number",
      +  "null"
      +]
    • removedOutput schema / properties / ok / anyOf
      Removed value: -[
      -  {
      -    "type": "boolean"
      -  },
      -  {
      -    "type": "null"
      -  }
      -]
    • addedOutput schema / properties / ok / type
      Added value: +[
      +  "boolean",
      +  "null"
      +]
    • removedOutput schema / properties / partial / anyOf
      Removed value: -[
      -  {
      -    "type": "boolean"
      -  },
      -  {
      -    "type": "null"
      -  }
      -]
    • addedOutput schema / properties / partial / type
      Added value: +[
      +  "boolean",
      +  "null"
      +]
    • changedOutput schema / properties / results / anyOf
      Previous value: -[
      -  {
      -    "items": {
      -      "additionalProperties": {},
      -      "properties": {
      -        "code": {
      -          "anyOf": [
      -            {
      -              "type": "string"
      -            },
      -            {
      -              "type": "null"
      -            }
      -          ]
      -        },
      -        "delistUrl": {
      -          "anyOf": [
      -            {
      -              "type": "string"
      -            },
      -            {
      -              "type": "null"
      -            }
      -          ]
      -        },
      -        "error": {
      -          "anyOf": [
      -            {
      -              "type": "string"
      -            },
      -            {
      -              "type": "null"
      -            }
      -          ]
      -        },
      -        "listKey": {
      -          "anyOf": [
      -            {
      -              "type": "string"
      -            },
      -            {
      -              "type": "null"
      -            }
      -          ]
      -        },
      -        "listed": {
      -          "anyOf": [
      -            {
      -              "type": "boolean"
      -            },
      -            {
      -              "type": "null"
      -            }
      -          ]
      -        },
      -        "name": {
      -          "anyOf": [
      -            {
      -              "type": "string"
      -            },
      -            {
      -              "type": "null"
      -            }
      -          ]
      -        },
      -        "reason": {
      -          "anyOf": [
      -            {
      -              "type": "string"
      -            },
      -            {
      -              "type": "null"
      -            }
      -          ]
      -        }
      -      },
      -      "type": "object"
      -    },
      -    "type": "array"
      -  },
      -  {
      -    "type": "null"
      -  }
      -]New value: +[
      +  {
      +    "items": {
      +      "additionalProperties": {},
      +      "properties": {
      +        "code": {
      +          "type": [
      +            "string",
      +            "null"
      +          ]
      +        },
      +        "delistUrl": {
      +          "type": [
      +            "string",
      +            "null"
      +          ]
      +        },
      +        "error": {
      +          "type": [
      +            "string",
      +            "null"
      +          ]
      +        },
      +        "listKey": {
      +          "type": [
      +            "string",
      +            "null"
      +          ]
      +        },
      +        "listed": {
      +          "type": [
      +            "boolean",
      +            "null"
      +          ]
      +        },
      +        "name": {
      +          "type": [
      +            "string",
      +            "null"
      +          ]
      +        },
      +        "reason": {
      +          "type": [
      +            "string",
      +            "null"
      +          ]
      +        }
      +      },
      +      "type": "object"
      +    },
      +    "type": "array"
      +  },
      +  {
      +    "type": "null"
      +  }
      +]
    • removedOutput schema / properties / total / anyOf
      Removed value: -[
      -  {
      -    "type": "number"
      -  },
      -  {
      -    "type": "null"
      -  }
      -]
    • addedOutput schema / properties / total / type
      Added value: +[
      +  "number",
      +  "null"
      +]
    • removedOutput schema / properties / zonesQueried / anyOf
      Removed value: -[
      -  {
      -    "type": "number"
      -  },
      -  {
      -    "type": "null"
      -  }
      -]
    • addedOutput schema / properties / zonesQueried / type
      Added value: +[
      +  "number",
      +  "null"
      +]
  2. Changed2 schema fields changed
    • addedOutput schema / properties / partial
      Added value: +{
      +  "anyOf": [
      +    {
      +      "type": "boolean"
      +    },
      +    {
      +      "type": "null"
      +    }
      +  ]
      +}
    • addedOutput schema / properties / zonesQueried
      Added value: +{
      +  "anyOf": [
      +    {
      +      "type": "number"
      +    },
      +    {
      +      "type": "null"
      +    }
      +  ]
      +}
  3. Changed1 schema field changed
    • changedOutput schema / (root)
      Previous value: -nullNew value: +{
      +  "$schema": "http://json-schema.org/draft-07/schema#",
      +  "additionalProperties": {},
      +  "properties": {
      +    "clean": {
      +      "anyOf": [
      +        {
      +          "type": "boolean"
      +        },
      +        {
      +          "type": "null"
      +        }
      +      ]
      +    },
      +    "ip": {
      +      "anyOf": [
      +        {
      +          "type": "string"
      +        },
      +        {
      +          "type": "null"
      +        }
      +      ]
      +    },
      +    "listedCount": {
      +      "anyOf": [
      +        {
      +          "type": "number"
      +        },
      +        {
      +          "type": "null"
      +        }
      +      ]
      +    },
      +    "ok": {
      +      "anyOf": [
      +        {
      +          "type": "boolean"
      +        },
      +        {
      +          "type": "null"
      +        }
      +      ]
      +    },
      +    "results": {
      +      "anyOf": [
      +        {
      +          "items": {
      +            "additionalProperties": {},
      +            "properties": {
      +              "code": {
      +                "anyOf": [
      +                  {
      +                    "type": "string"
      +                  },
      +                  {
      +                    "type": "null"
      +                  }
      +                ]
      +              },
      +              "delistUrl": {
      +                "anyOf": [
      +                  {
      +                    "type": "string"
      +                  },
      +                  {
      +                    "type": "null"
      +                  }
      +                ]
      +              },
      +              "error": {
      +                "anyOf": [
      +                  {
      +                    "type": "string"
      +                  },
      +                  {
      +                    "type": "null"
      +                  }
      +                ]
      +              },
      +              "listKey": {
      +                "anyOf": [
      +                  {
      +                    "type": "string"
      +                  },
      +                  {
      +                    "type": "null"
      +                  }
      +                ]
      +              },
      +              "listed": {
      +                "anyOf": [
      +                  {
      +                    "type": "boolean"
      +                  },
      +                  {
      +                    "type": "null"
      +                  }
      +                ]
      +              },
      +              "name": {
      +                "anyOf": [
      +                  {
      +                    "type": "string"
      +                  },
      +                  {
      +                    "type": "null"
      +                  }
      +                ]
      +              },
      +              "reason": {
      +                "anyOf": [
      +                  {
      +                    "type": "string"
      +                  },
      +                  {
      +                    "type": "null"
      +                  }
      +                ]
      +              }
      +            },
      +            "type": "object"
      +          },
      +          "type": "array"
      +        },
      +        {
      +          "type": "null"
      +        }
      +      ]
      +    },
      +    "total": {
      +      "anyOf": [
      +        {
      +          "type": "number"
      +        },
      +        {
      +          "type": "null"
      +        }
      +      ]
      +    }
      +  },
      +  "type": "object"
      +}
  4. First observed

TDQS

A4.7/5.0
Behavior5/5

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

Goes well beyond the readOnly/openWorld annotations: it discloses that slow lists are skipped and surface as partial=true (provisional verdicts), that a call is a point-in-time snapshot only, and that the tool is anonymous with the strictest per-IP rate limit of the anonymous tools. Auth and rate-limit context like this is exactly what annotations cannot convey.

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?

Front-loaded with purpose, then tightly layered caveats (input type, partial results, snapshot semantics, rate limit). Four dense sentences, none of which repeat the schema or waste space.

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?

With an output schema present the description needn't explain returns, yet it still frames what a verdict means (clean flag, partial results, snapshot nature). Nothing an agent needs to call and interpret this tool 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% and the single param is already documented as 'Public IPv4 or IPv6 address', so the baseline is 3. The description adds real meaning by stressing the input must be an IP rather than a domain and by tying the parameter to what the check actually consumes.

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 ('Checks a public IP address against common DNS blocklists') plus the return shape (per-list listed status, reason code, delisting URL, totals, clean flag). It also explicitly distinguishes itself from siblings by noting it takes an IP, not a domain, naming mx_lookup and check_dns as the resolvers.

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 gives a clear input boundary and routes domain-based needs to mx_lookup or check_dns, which functions as an explicit when-not plus alternative. It does not, however, spell out the positive use case (e.g., deliverability/reputation triage) that would tell an agent when this tool is the right first call.

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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