net-mcp

Local Arp

local_arp

View the ARP cache to map IP addresses to MAC addresses and identify devices on the local network segment. No admin privileges required.

Instructions

Show the ARP table (IP-to-MAC address mappings).

Displays cached ARP entries for the local network. Useful for seeing what hosts are on the same L2 segment. Does not require admin privileges.

Input Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Output Schema

TableJSON Schema

Name	Required	Description
`note`	No	Additional context about the result
`error`	No	Why the tool could not produce a result: input validation failure, tool disabled by configuration, binary not installed, or no service answered. Empty when the command executed.
`stderr`	Yes	Standard error of the command, or the failure message when the command did not run
`stdout`	Yes	Standard output of the command (curl output is capped at 10,000 characters)
`command`	Yes	The exact command line that was executed, or the tool name if the command never ran
`success`	Yes	True when the command ran and exited with status 0
`platform`	Yes	Operating system the command ran on (Darwin, Linux or Windows)
`returncode`	Yes	Process exit status. 0 = success; 2 = input rejected before running; 124 = timed out; 126 = disabled by config or permission denied; 127 = binary not found

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Sep 22, 2026

TDQS

A4.5/5.0

Behavior4/5

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

With no annotations, the description carries the behavioral burden. It discloses that entries are cached, that the scope is the local network/L2 segment, and that no admin privileges are required. This gives an agent useful expectations for a read-only command.

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?

Three short sentences, each earning its place: what is shown, what it means, and the privilege requirement. No filler or repetition.

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 zero-argument, read-only ARP inspection tool with an output schema, the description covers operation, scope, cache behavior, use case, and privilege requirements. Nothing essential is missing.

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?

The input schema has zero parameters, so there are no parameter semantics to document; the rubric baseline of 4 applies. The description's no-arguments framing is implicitly consistent with the empty 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 uses a precise verb ('Show') and concrete resource ('ARP table (IP-to-MAC address mappings)'), then clarifies it displays cached entries for the local network/L2 segment. This cleanly differentiates it from sibling tools like local_routes or local_connections.

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 gives a clear use case: 'seeing what hosts are on the same L2 segment.' It does not explicitly name alternatives or say when not to use it, but for a uniquely scoped local diagnostic the guidance is sufficient.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.