calc.engineer

rack capacity

rack_capacity

Quick rack space and weight sizing calculator for homelab and small data center racks. Enter your devices with their height in rack units, weight, and wattage to get total utilization, remaining free space, weight totals in lbs and kg, and recommended PDU count based on the NEC 80% continuous load rule (1920W per 20A/120V PDU). Estimates cable management overhead at 2U per 10U of installed gear. Outputs total_watts that chains into power_cost and cooling_btu for full infrastructure planning.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`devices`	Yes	List of devices to place in the rack
`rack_units`	No	Total rack height in rack units (standard is 42U)

Output Schema

TableJSON Schema

Name	Required	Description
`free_u`	Yes	Remaining empty rack units
`used_u`	Yes	Total rack units consumed by devices
`overhead_u`	Yes	Estimated cable management overhead in rack units (2U per 10U of gear)
`total_watts`	Yes	Total power draw of all devices in watts
`total_weight_kg`	Yes	Total weight of all devices in kilograms
`utilization_pct`	Yes	Percentage of rack space used by devices
`effective_free_u`	Yes	Free rack units after subtracting cable management overhead
`total_weight_lbs`	Yes	Total weight of all devices in pounds
`recommended_pdu_count`	Yes	Recommended number of PDUs (each PDU = 80% of 20A/120V = 1920W)

TDQS

A4.6/5.0

Behavior5/5

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

With no annotations provided, the description fully discloses behavior: it calculates total utilization, free space, weight totals, and PDU count using NEC 80% rule, estimates cable overhead at 2U per 10U, and outputs total_watts for chaining. No side effects or destructive actions are implied, which matches a read-only calculator.

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 three sentences long, front-loaded with a clear purpose. Each sentence adds essential information: purpose, inputs/outputs, and chaining. No redundancy or filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

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 full schema coverage, the description adequately explains key outputs and rules. The existence of an output schema compensates for not detailing return structure. However, it could briefly mention that results are per-device and aggregated, though not critical.

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 parameters are defined. The description adds significant value by explaining how inputs are used (e.g., height in U, weight in lbs, wattage) and contextual rules (cable overhead, NEC rule). This enhances meaning beyond the schema alone.

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 identifies the tool as a 'rack space and weight sizing calculator' for homelab and small data center racks. It specifies the exact inputs (device height in U, weight, wattage) and outputs (utilization, free space, weight totals, PDU count, total_watts). This distinguishes it from sibling calculator tools by detailing its unique functionality and output chaining.

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 states the tool is for 'quick' sizing in 'homelab and small data center racks' and mentions integration with power_cost and cooling_btu, guiding workflow. However, it does not explicitly state when to avoid this tool or suggest alternatives (e.g., for pure power calculations), leaving some ambiguity.

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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