calc.engineer

rc filter

rc_filter

Computes the cutoff frequency, time constant, impedance, and phase shift of a first-order RC filter. Supports both lowpass and highpass topologies. The cutoff frequency is f = 1/(2piRC) where the signal is attenuated by 3 dB. The time constant tau = RC governs transient response — the capacitor reaches 63.2% of its final value after one tau. Use for anti-aliasing before ADCs, DC blocking, noise filtering, and signal conditioning. Chain from voltage_divider to design filtered bias networks.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`filter_type`	No	Filter topology: 'lowpass' (R then C to ground) or 'highpass' (C then R to ground).	lowpass
`capacitance_f`	Yes	Capacitance in farads (C). The capacitive element of the RC filter.
`resistance_ohm`	Yes	Resistance in ohms (R). The resistive element of the RC filter.

Output Schema

TableJSON Schema

Name	Required	Description
`cutoff_freq_hz`	Yes	Cutoff frequency (-3 dB point) in hertz.
`cutoff_freq_khz`	Yes	Cutoff frequency in kilohertz for convenience.
`time_constant_s`	Yes	RC time constant (tau) in seconds.
`time_constant_ms`	Yes	RC time constant in milliseconds.
`phase_at_cutoff_deg`	Yes	Phase shift at the cutoff frequency in degrees. -45 for lowpass, +45 for highpass.
`impedance_at_cutoff_ohm`	Yes	Total impedance magnitude at the cutoff frequency in ohms. Equals R * sqrt(2) for a first-order RC filter.

TDQS

A4.2/5.0

Behavior4/5

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

Discloses key formulas (f=1/(2πRC), τ=RC) and the 3 dB point and 63.2% transient behavior. No annotations exist, so description carries full burden; it provides sufficient behavioral context for correct invocation.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Single paragraph but well-organized: starts with purpose, then formulas, then use cases, then chaining hint. Every sentence adds value; no fluff.

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?

Covers inputs, formulas, topology, use cases, and chaining. Output schema exists (not shown but indicated), so return values need not be described. Fully adequate for a first-order RC filter calculator.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so baseline is 3. Description adds formulas and uses for parameters (e.g., 'capacitive element') but does not significantly extend beyond schema definitions.

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 it computes cutoff frequency, time constant, impedance, and phase shift for first-order RC filters, supporting both lowpass and highpass topologies. It distinguishes from sibling tools like voltage_divider and lc_resonance by specifying the RC filter focus and suggesting chaining from voltage_divider.

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?

Provides explicit use cases: anti-aliasing, DC blocking, noise filtering, signal conditioning. Also suggests chaining with voltage_divider for bias networks. However, it does not explicitly state when not to use or compare to alternative filter types.

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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