Tengu

by rfunix

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Python

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rustscan_scan

Perform fast port scanning across all 65,535 ports, then automatically use Nmap to detect services.

Instructions

Perform ultra-fast port scanning using RustScan.

RustScan can scan all 65535 ports in seconds by using async I/O, then passes discovered open ports to Nmap for service detection.

Args: target: Target IP address or hostname. ports: Port specification (e.g. "80,443" or "1-65535"). batch_size: Number of ports to scan per batch (default 1500, max 65535). timeout: Override scan timeout in seconds.

Returns: Discovered open ports and basic service information.

Note: - Target must be in tengu.toml [targets].allowed_hosts. - High batch_size values may trigger IDS/IPS alerts.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "target": "<target>"
    },
    "name": "rustscan_scan"
  }
}

Input Schema

Name	Required	Default
`ports`	No	1-65535
`target`	Yes
`timeout`	No
`batch_size`	No

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.3.1Aug 2, 2026

TDQS

A4.5/5.0

Behavior4/5

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It reveals the async I/O approach, the handoff to Nmap, the allowed_hosts restriction, and the potential for IDS/IPS alerts. It also specifies the return value ('Discovered open ports and basic service information'). While it doesn't mention resource consumption or non-destructive behavior, the disclosed traits are relevant and go beyond a simple scan description.

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?

The description is well-structured with clear sections: purpose, explanatory sentence, Args, Returns, and Notes. It is slightly verbose in the marketing-like claim ('scan all 65535 ports in seconds by using async I/O'), but that adds context. Overall, every sentence contributes to understanding, though it could be tightened.

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 moderate complexity and the presence of an output schema, the description is thorough. It covers the purpose, parameters, return value, allowed_hosts prerequisite, and a side-effect warning (IDS/IPS alerts). No critical gaps remain for an agent to select and invoke the tool correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters5/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The input schema has no per-property descriptions (0% coverage), so the description is essential. It explains each of the four parameters: target as IP/hostname, ports with examples ('80,443' or '1-65535'), batch_size with default and max, and timeout as an override in seconds. This adds substantial meaning beyond the schema's raw types and defaults.

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 opens with a specific verb+resource: 'Perform ultra-fast port scanning using RustScan.' It also explains the tool's distinct role by noting that it passes discovered open ports to Nmap for service detection, clearly differentiating it from sibling tools like nmap_scan and masscan_scan. The purpose is unambiguous and specific.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides clear context for when to use the tool: 'ultra-fast' port scanning with subsequent Nmap service detection. It also mentions a prerequisite: target must be in tengu.toml allowed_hosts, and warns that high batch_size may trigger IDS/IPS alerts. However, it does not explicitly state when not to use this tool or compare it to alternatives like nmap_scan or masscan_scan, so it lacks explicit exclusions.

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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