calc.engineer

led resistor

led_resistor

Calculates the current-limiting resistor for driving one or more LEDs in series from a DC supply. Computes the exact resistance from R = (Vsupply - n*Vf) / I, then selects the nearest E24 standard resistor value. Reports the actual current with the standard resistor, power dissipation, and voltage across the resistor. Supports series LED strings by specifying led_count. Validates that supply voltage exceeds total forward voltage. Chain from ohms_law for power budgeting or into trace_width for PCB layout.

Input Schema

TableJSON Schema

Name	Required	Description
`led_count`	No	Number of LEDs in series. Defaults to 1.
`led_forward_v`	No	LED forward voltage in volts (V). Defaults to 2.0V (typical red LED).
`led_current_ma`	No	Desired LED current in milliamps (mA). Defaults to 20mA.
`supply_voltage_v`	Yes	Supply voltage in volts (V). Must be positive.

Output Schema

TableJSON Schema

Name	Required	Description
`resistance_ohm`	Yes	Exact calculated resistance in ohms.
`nearest_e24_ohm`	Yes	Nearest standard E24 series resistor value in ohms.
`actual_current_ma`	Yes	Actual LED current in milliamps (mA) when using the nearest E24 resistor.
`power_dissipation_mw`	Yes	Power dissipated by the resistor in milliwatts (mW), using the E24 value.
`voltage_across_resistor_v`	Yes	Voltage drop across the current-limiting resistor in volts.

TDQS

A4.7/5.0

Behavior5/5

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

With no annotations, the description fully discloses behavior: computes exact resistance, selects nearest E24 standard, reports actual current, power dissipation, voltage across resistor, and validates voltage. No contradictions.

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?

Four sentences, front-loaded with purpose, then computation, outputs, validation, and chaining. Every sentence adds value without redundancy.

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 presence of an output schema, the description adequately covers inputs, validation, outputs, and related tools. It is complete for an electronics calculation tool.

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% with parameter descriptions. The description adds value beyond schema by explaining the formula, standard resistor selection, and output reports, though it does not describe each parameter in depth.

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 the current-limiting resistor for LEDs in series from a DC supply, names the formula, and specifies outputs. It is distinct from sibling tools by focusing on this specific task.

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 usage context, including validation of supply voltage and suggestions to chain with ohms_law or trace_width. It does not explicitly list when not to use or compare to all alternatives, but 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.

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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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