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dnsbl_check

Read-only

Query a public IP address against common DNS blacklists and return, per list, whether it is listed, the reason code the list gave and its delisting URL, plus totals and a clean flag. Takes an IP address, not a domain: resolve the sending host first with mx_lookup or check_dns. Slow blocklists are dropped instead of waited for, so partial=true means zonesQueried is below total and a clean verdict is provisional for the lists that never answered. A listing usually appears between checks, so one call proves only this moment. Anonymous and rate-limited per IP, and this is the strictest limit of the anonymous tools.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
ipYesPublic IPv4 or IPv6 address

Output Schema

TableJSON 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

A4.9/5.0
Behavior5/5

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

Annotations already declare readOnlyHint=true, but the description goes far beyond that: it explains partial=true when slow blocklists are dropped, notes that a clean verdict is provisional for unanswered lists, warns that listings are transient, and states the rate-limiting and anonymity constraints. This is rich behavioral context that an agent would otherwise lack.

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?

The description is front-loaded with the tool's purpose and return shape, then proceeds to caveats in a logical order. Every sentence carries distinct, necessary information (input type, partial behavior, transience, rate limits) without redundant phrasing.

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?

Given the existence of an output schema, the description is not required to re-explain return values, yet it complements them by clarifying the meaning of partial results and the provisional nature of a clean verdict. It also covers input expectations, operational constraints, and the need to resolve the host first, making the definition complete for an agent to call it correctly.

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?

The schema fully documents the single 'ip' parameter as a public IPv4 or IPv6 address (100% coverage). The description adds valuable meaning by emphasizing that it takes an IP address, not a domain, and directing the agent to resolve the sending host first, which clarifies intended input beyond the schema text.

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 and resource: query a public IP against DNS blacklists and return per-list results plus totals and a clean flag. It distinguishes itself from siblings by explicitly noting it takes an IP, not a domain, and names mx_lookup and check_dns as alternative tools for resolving the host.

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 when-to-use guidance: resolve the sending host first with mx_lookup or check_dns, then use this tool. It also discloses operational limits (anonymous, rate-limited per IP, strictest anonymous limit) and explains that a single call proves only the current moment, which directly affects when the result is meaningful.

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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