calc.engineer

capacitor charge

capacitor_charge

Calculates RC capacitor charge timing, energy storage, and transient voltages. Given resistance, capacitance, supply voltage, and optional initial voltage, computes the RC time constant (τ = R×C), time to reach standard charge thresholds (63%, 86%, 95%, 99%), voltage at key time points, energy stored (E = ½CV²), and peak charging current. Optionally calculates time to reach a specific target voltage using t = -τ × ln((Vsupply - Vtarget) / (Vsupply - Vinitial)). Essential for timing circuits, power-on reset delays, debounce networks, and soft-start designs. Chain from rc_filter for frequency-domain analysis or timer_555 for oscillator timing.

Input Schema

TableJSON Schema

Name	Required	Description
`v_supply`	Yes	Supply voltage in volts. The voltage the capacitor charges toward.
`v_target`	No	Target voltage to reach in volts (optional). When provided, calculates time to reach this voltage. Must be between v_initial and v_supply.
`v_initial`	No	Initial capacitor voltage in volts (default 0 for fully discharged).
`capacitance_f`	Yes	Capacitance in farads (C). Use scientific notation, e.g. 1e-6 for 1 µF.
`resistance_ohm`	Yes	Series resistance in ohms (R). Controls charge/discharge rate.

Output Schema

TableJSON Schema

Name	Required	Description
`tau_s`	Yes	RC time constant (τ = R×C) in seconds.
`tau_ms`	Yes	RC time constant in milliseconds.
`energy_mj`	Yes	Energy stored at full charge in millijoules.
`v_at_1tau`	Yes	Capacitor voltage after 1τ in volts.
`v_at_2tau`	Yes	Capacitor voltage after 2τ in volts.
`v_at_5tau`	Yes	Capacitor voltage after 5τ in volts.
`energy_joules`	Yes	Energy stored at full charge: E = ½CV² in joules.
`peak_current_ma`	Yes	Peak charging current at t=0 in milliamps: Ipeak = (Vsupply − Vinitial) / R.
`time_to_63pct_ms`	Yes	Time to reach 63.2% of (Vsupply − Vinitial) in milliseconds (1τ).
`time_to_86pct_ms`	Yes	Time to reach 86.5% of (Vsupply − Vinitial) in milliseconds (2τ).
`time_to_95pct_ms`	Yes	Time to reach 95.0% of (Vsupply − Vinitial) in milliseconds (3τ).
`time_to_99pct_ms`	Yes	Time to reach 99.3% of (Vsupply − Vinitial) in milliseconds (5τ).
`time_to_target_ms`	Yes	Time to reach v_target in milliseconds (null if v_target not specified).

TDQS

A4.5/5.0

Behavior4/5

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

No annotations provided; description carries full burden. It discloses formulas, outputs, and optional target voltage calculation. No destructive behavior expected, so transparency is sufficient.

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 sentences pack all essential information: purpose, outputs, optional behavior, and use cases. No fluff; every sentence earns its place.

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?

Output schema exists, covering return values. Description covers inputs, purpose, and usage context completely for a 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%, so baseline is 3. The description adds value by summarizing formulas and relationships (τ=R×C, E=½CV², t= -τ ln(...)), providing context beyond individual parameter 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 RC capacitor charge timing, energy storage, and transient voltages, listing specific outputs. It distinguishes from sibling tools by mentioning chaining from rc_filter and timer_555, providing a specific verb and resource.

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?

It explicitly lists use cases (timing circuits, power-on reset delays, debounce networks, soft-start designs) and suggests chaining from rc_filter or timer_555, giving clear context. Missing explicit when-not-to-use, but adequate.

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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