calc.engineer

wireguard mtu

wireguard_mtu

Calculate the optimal MTU for a WireGuard VPN tunnel interface with a detailed overhead breakdown. Accounts for WireGuard header (32 bytes), outer IP header (20 bytes IPv4 or 40 bytes IPv6), UDP header (8 bytes), and optional PPPoE encapsulation (8 bytes). Prevents fragmentation and PMTUD black holes by computing the maximum inner packet size that fits within the physical link MTU. Essential for WireGuard setup on residential ISP connections (PPPoE), IPv6 tunnels, and any VPN where incorrect MTU causes slow or stalled connections.

Input Schema

TableJSON Schema

Name	Required	Description
`ipv6`	No	Whether the outer (transport) IP header uses IPv6 (40 bytes) instead of IPv4 (20 bytes)
`over_pppoe`	No	Whether the link uses PPPoE encapsulation (adds 8 bytes of overhead)
`interface_mtu`	No	MTU of the underlying physical or virtual network interface in bytes

Output Schema

TableJSON Schema

Name	Required	Description
`breakdown`	Yes	Itemized breakdown of each overhead component in bytes
`wireguard_mtu`	Yes	Optimal MTU to set on the WireGuard tunnel interface in bytes
`overhead_bytes`	Yes	Total encapsulation overhead in bytes subtracted from interface MTU

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 fully discloses behavior: calculates max inner packet size considering various overheads (WireGuard header, IP, UDP, PPPoE) and prevents fragmentation. It explains the computation's purpose and benefits.

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 four concise sentences with clear structure: purpose, technical details, result explanation, and usage context. No extraneous information.

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 low complexity and complete input schema, the description fully covers what the tool does, what inputs mean, and when to use it. The presence of an output schema further reduces need for return value explanation.

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%, but the description adds value by explaining the overhead contribution of each parameter (e.g., IPv4 vs IPv6, PPPoE encapsulation) and their impact on the calculation, going beyond schema descriptions.

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 calculates optimal MTU for WireGuard VPN, specifying the resource and action. It distinguishes from sibling calculators by focusing on WireGuard MTU with overhead breakdown.

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 explicit usage scenarios: residential ISP connections (PPPoE), IPv6 tunnels, and any VPN with MTU issues. It does not explicitly state when not to use, but context is clear among diverse sibling tools.

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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TDQS

A3.9/5.0

Disambiguation4/5

Despite 89 tools, each has a clearly distinct purpose with detailed descriptions that often reference related tools. Overlap exists (e.g., multiple LoRa/RF tools), but the descriptions are sufficient to distinguish them. Some confusion possible among similar-sounding tools like attenuator_pi and attenuator_tee, but the descriptions explicitly compare them.

Naming Consistency4/5

Consistent underscore-separated lowercase naming. Most tools follow a verb_noun pattern (e.g., capacitor_charge, wire_gauge) or noun_noun (power_cost). Minor inconsistencies such as 'bmi_calculator' vs 'solar_sizing' but overall predictable.

Tool Count2/5

89 tools is far too many for a single MCP server. This scope is more appropriate for multiple specialized servers. The sheer number will slow agent selection and increase cognitive load, reducing coherence.

Completeness3/5

Covers many domains (RF, solar, PCB, networking, math, etc.) but lacks depth in some areas (e.g., no three-phase power, no airflow calculations). Some domains have comprehensive coverage (LoRa/Meshtastic), but others feel incomplete for the tool count.

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