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Kastell

Kastell

Official
by kastelldev
OverviewSchemaSourceRelated ServersDiscussionsAdmin
TypeScript
Hybrid

server_lock

Destructive

Harden a server to production standard by applying 24 hardening steps in a single SSH session, covering SSH, fail2ban, UFW, Docker, and more, with audit score comparison.

Instructions

Harden a server to production standard. Applies 24 hardening steps in a single SSH session covering SSH, fail2ban, UFW, sysctl, unattended-upgrades, Docker daemon, auditd, AIDE, and more. Requires production=true (safety gate). Pass dryRun=true to preview. Platform-aware: preserves Coolify/Dokploy ports. Shows audit score before and after. Requires SSH access. For fine-grained SSH/firewall/domain changes use server_secure instead.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "server_lock"
  }
}

Input Schema

NameRequiredDescriptionDefault
forceNoForce lock even if server already appears hardened.
dryRunNoPreview changes without applying. Returns what would be done. Bypasses the production safety gate.
serverNoServer name or IP. Auto-selected if only one server exists.
productionNoSet to true to confirm hardening intent. Required to apply 19 hardening steps (safety gate). Omit or pass false to preview with dryRun=true.

Output Schema

NameRequiredDescriptionDefault
resultYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv2.2.4
    • changedOutput schema / (root)
      Previous value: -nullNew value: +{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "additionalProperties": false,
+  "properties": {
+    "result": {
+      "additionalProperties": false,
+      "properties": {
+        "scoreAfter": {
+          "type": "number"
+        },
+        "scoreBefore": {
+          "type": "number"
+        },
+        "stepErrors": {
+          "additionalProperties": {},
+          "propertyNames": {
+            "type": "string"
+          },
+          "type": "object"
+        },
+        "steps": {
+          "type": "number"
+        },
+        "success": {
+          "type": "boolean"
+        }
+      },
+      "required": [
+        "success",
+        "steps",
+        "scoreBefore",
+        "scoreAfter"
+      ],
+      "type": "object"
+    }
+  },
+  "required": [
+    "result"
+  ],
+  "type": "object"
+}
  2. First observedv1.14.0

TDQS

A4.8/5.0
Behavior5/5

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

Description adds context beyond annotations: mentions 24 hardening steps, platform-awareness (preserving Coolify/Dokploy ports), and shows audit score before/after. Annotations already indicate destructiveHint=true, which aligns.

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?

Description is a single paragraph front-loaded with main purpose, then specifics. Efficient but could be slightly more concise (e.g., '24 hardening steps' is repeated notion). Still very good.

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 (24 steps), the description covers purpose, usage, parameters, behavior, and prerequisites. Output schema exists so return values are handled. No gaps.

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%, so baseline 3. Description enhances understanding: production as safety gate, dryRun previews and bypasses gate, force overrides hardened check. Adds meaning beyond schema.

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 clearly states the tool hardens a server to production standard, lists specific components (SSH, fail2ban, UFW, etc.), and distinguishes from sibling tool server_secure by mentioning fine-grained changes.

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?

Explicitly provides when to use (full hardening) and when not (fine-grained changes, use server_secure). Also mentions prerequisites like SSH access and safety gate production=true.

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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