Dechonet MCP

Subdomain Discovery

subdomain_discovery

Read-onlyIdempotent

Discover a domain's subdomains from public Certificate Transparency logs passively, flag risky operational names, and map attack surface before deeper security recon.

Instructions

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

TableJSON 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

TableJSON 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.

Changed2 schema fields changedv1.5.14Oct 15, 2026

addedOutput schema / properties / observation

Added value: +{
+  "additionalProperties": false,
+  "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"
+    }
+  },
+  "required": [
+    "state",
+    "observedAt",
+    "cached",
+    "ageMinutes"
+  ],
+  "type": "object"
+}

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": {
+    "additionalProperties": false,
+    "properties": {
+      "id": {
+        "type": "string"
+      },
+      "tool": {
+        "type": "string"
+      },
+      "url": {
+        "type": "string"
+      }
+    },
+    "required": [
+      "tool",
+      "id",
+      "url"
+    ],
+    "type": "object"
+  },
+  "type": "array"
+}

Addedv1.1.0Sep 8, 2026

TDQS

A4.6/5.0

Behavior5/5

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

Annotations cover the safety profile (readOnly, idempotent, non-destructive, openWorld), and the description adds materially beyond that: full passivity with the justification (no packets sent, CT logs are public), no API key required, rate-limiting, and which name patterns it flags. These are operational traits an agent cannot infer from structured fields.

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 action and purpose, and most sentences earn their place (passivity rationale, alternative routing). The final sentence enumerating return values is somewhat redundant given an output schema exists, which keeps this just below a 5.

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?

For a one-parameter, read-only reconnaissance tool, the description covers purpose, safety, prerequisites, sibling routing, and expected output shape. An agent has everything needed to select and invoke it correctly.

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 description coverage is 100% and the single 'domain' parameter is well documented (registrable domain, no scheme/path). The description adds no syntax or format detail beyond the schema, so the baseline 3 applies when the schema already does the work.

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 (enumerate), resource (subdomains), and source mechanism (Certificate Transparency logs), which is far more than a restatement of the name. It explicitly contrasts itself against siblings by naming dns_lookup and lookalike_domains, so an agent can route without opening either 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?

"Use this as the first recon step to map a domain's attack surface" gives explicit positioning, and it names two alternatives with the condition that selects each (dns_lookup for resolution checks, lookalike_domains for typosquats). Nothing about when-to-use 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.