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ASN / BGP Lookup

asn_lookup
Read-onlyIdempotent

Look up Autonomous System (ASN) / BGP information for an IP address or AS number: the network operator, announced prefixes, abuse contact, and a classification (cloud, CDN, ISP, hosting, or enterprise). For an IPv4 address it also reports whether the address is on the Tor Project exit list or in a VPN provider or datacenter range (X4BNet lists_vpn), as information that does not change the result. Use this to identify who runs a network or whether an IP is cloud/CDN-hosted. Use reverse_dns instead for the host-level PTR name of a single IP. Read-only; requires no API key; rate-limited. Returns operator, prefixes, classification, and abuse contact.

Input Schema

NameRequiredDescriptionDefault
queryYesAn IP address (e.g., '1.1.1.1') or an AS number in 'AS####' form (e.g., 'AS13335').

Output Schema

NameRequiredDescriptionDefault
kpisNoKey metrics as label/value pairs
gradeNoLetter grade (A+ to F) when the tool grades the target
scoreNo0-100 score when the tool scores the target
issuesNoDetected problems, severity-rated
statusYesOverall verdict, e.g. 'good' | 'warning' | 'bad' | 'info' | 'unknown'
actionsNoRecommended next actions, most important first
summaryNoOne-paragraph interpretation of the result
receiptsNoSigned observation receipts behind this result, one per lookup: when, from where and under which rules version DechoNet observed it. Each url shows the record and checks its Ed25519 signature.
reportUrlYesHuman-facing interactive report for this exact lookup on dechonet.com
observationNoHow much was actually observed and when. A partial observation means some checks did not answer: missing parts are not verified, never clean.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changed
    • addedOutput schema / properties / receipts
      Added value: +{
      +  "description": "Signed observation receipts behind this result, one per lookup: when, from where and under which rules version DechoNet observed it. Each url shows the record and checks its Ed25519 signature.",
      +  "items": {
      +    "properties": {
      +      "id": {
      +        "type": "string"
      +      },
      +      "tool": {
      +        "type": "string"
      +      },
      +      "url": {
      +        "type": "string"
      +      }
      +    },
      +    "required": [
      +      "tool",
      +      "id",
      +      "url"
      +    ],
      +    "type": "object"
      +  },
      +  "type": "array"
      +}
  2. Changed1 schema field changed
    • addedOutput schema / properties / observation
      Added value: +{
      +  "description": "How much was actually observed and when. A partial observation means some checks did not answer: missing parts are not verified, never clean.",
      +  "properties": {
      +    "ageMinutes": {
      +      "type": [
      +        "number",
      +        "null"
      +      ]
      +    },
      +    "cached": {
      +      "type": "boolean"
      +    },
      +    "observedAt": {
      +      "type": [
      +        "string",
      +        "null"
      +      ]
      +    },
      +    "state": {
      +      "enum": [
      +        "complete",
      +        "partial",
      +        "unknown"
      +      ],
      +      "type": "string"
      +    }
      +  },
      +  "type": "object"
      +}
  3. First observed

TDQS

A4.3/5.0
Behavior4/5

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

Annotations already declare readOnly/idempotent/non-destructive, so the bar is lower, yet the description adds real context: no API key required, rate-limited, and that Tor exit / VPN / datacenter flags are informational and do not alter the result. It stops short of describing pagination or lookup-failure behavior, so not a 5.

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?

Front-loaded with the core purpose and the alternative routing early. Slightly dense in the middle (the X4BNet parenthetical and the trailing 'Returns ...' sentence) but every clause carries information.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists, so the description need not explain returns, and it mostly avoids doing so. The closing 'Returns operator, prefixes, classification, and abuse contact' partially duplicates the output schema, a minor redundancy rather than a gap.

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?

Single parameter with 100% schema coverage, so the schema already documents both the IP and 'AS####' forms. The description adds no syntax or format detail beyond that; baseline 3 applies.

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?

Specific verb+resource with enumerated output scope (operator, prefixes, abuse contact, classification) and it names the sibling it is not (reverse_dns). An agent can distinguish it from ip_info or reverse_dns without opening the 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?

States the decision rule explicitly ('identify who runs a network or whether an IP is cloud/CDN-hosted') and names the alternative with its condition ('Use reverse_dns instead for the host-level PTR name of a single IP'). Nothing is left to inference.

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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