Dechonet-MCP

Subdomain Discovery

subdomain_discovery

Read-onlyIdempotent

Enumerate the subdomains of a domain from Certificate Transparency logs — fully passive (no packets are sent to the target; CT logs are public records of every TLS certificate ever issued). Flags operational-looking names (dev, staging, admin, vpn, legacy) and wildcard certificates, because forgotten subdomains are a common takeover path. Use this as the first recon step to map a domain's attack surface. Use dns_lookup to check whether a discovered name still resolves, or lookalike_domains for typosquat variants of the domain name itself. Read-only; requires no API key; rate-limited. Returns the subdomain count, risky-name count, wildcard flag, and the hostname list.

Input Schema

Name	Required	Description	Default
`domain`	Yes	Registrable domain to enumerate (e.g., 'example.com'), without scheme or path. Subdomains found in CT logs for this domain are returned.

Output Schema

Name	Required	Description
`kpis`	No	Key metrics as label/value pairs
`grade`	No	Letter grade (A+ to F) when the tool grades the target
`score`	No	0-100 score when the tool scores the target
`issues`	No	Detected problems, severity-rated
`status`	Yes	Overall verdict, e.g. 'good' \| 'warning' \| 'bad' \| 'info' \| 'unknown'
`actions`	No	Recommended next actions, most important first
`summary`	No	One-paragraph interpretation of the result
`receipts`	No	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.
`reportUrl`	Yes	Human-facing interactive report for this exact lookup on dechonet.com
`observation`	No	How 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.

Changed1 schema field changedOct 15, 2026

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"
+}

Changed1 schema field changedOct 15, 2026

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"
+}

AddedSep 2, 2026

TDQS

A4.7/5.0

Behavior4/5

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

Although annotations declare readOnlyHint=true and destructiveHint=false, the description adds meaningful context: 'fully passive (no packets are sent to the target)', 'requires no API key', and 'rate-limited'. It also lists return fields (subdomain count, risky-name count, wildcard flag, hostname list), which goes beyond typical annotation coverage. A 4 rather than 5 because it doesn't detail rate-limit thresholds or error conditions.

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 core action, then progressively adds passivity, flagging rationale, usage guidance, alternatives, and output summary. Every sentence contributes essential information with no fluff.

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 tool's complexity and the presence of an output schema, the description covers purpose, passivity, flagging logic, workflow position, alternatives, constraints (no API key, rate limits), and return summary. Nothing significant is missing for correct invocation.

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% for the single 'domain' parameter, so baseline is 3. The description adds value by explaining that the domain should be registrable and that subdomains found in CT logs are returned, giving contextual meaning beyond the schema's format example.

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 'Enumerate' and resource 'subdomains of a domain' and explains the source (Certificate Transparency logs). It explicitly distinguishes itself from siblings dns_lookup and lookalike_domains by naming them and their different roles.

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 ('Use this as the first recon step to map a domain's attack surface') and names alternatives: dns_lookup for resolving discovered names and lookalike_domains for typosquat variants. It leaves no ambiguity about its position in the workflow.

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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