calc.engineer

timer 555

timer_555

Calculates timing parameters for the ubiquitous NE555 / LM555 timer IC in astable (free-running oscillator) and monostable (one-shot pulse) modes. In astable mode, computes frequency, period, duty cycle, and HIGH/LOW durations from R1, R2, and C using f = 1.44 / ((R1 + 2·R2) · C). In monostable mode, computes pulse width from R and C using t = 1.1 · R · C. Standard 555 astable duty cycle is always >50%; for 50% duty cycle use a diode across R2. Useful for generating clock signals, PWM, delays, and debounce circuits. Chain from ohms_law for power calculations or resistor_color_code for component selection.

Input Schema

TableJSON Schema

Name	Required	Description
`mode`	Yes	Operating mode. 'astable' produces a continuous square wave. 'monostable' produces a single timed pulse.
`r1_ohm`	Yes	Resistance R1 in ohms. In astable mode this is the charge-path resistor between Vcc and the discharge pin. In monostable mode this is the timing resistor.
`r2_ohm`	No	Resistance R2 in ohms (astable mode only). Charge/discharge resistor between the discharge and threshold pins. Required for astable mode.
`c_farad`	Yes	Timing capacitor in farads. Typical values range from 1 pF to 1000 µF. Use scientific notation, e.g. 1e-6 for 1 µF.

Output Schema

TableJSON Schema

Name	Required	Description
`mode`	Yes	Operating mode used for calculation.
`r1_ohm`	Yes	R1 value used in ohms.
`r2_ohm`	Yes	R2 value used in ohms (null for monostable).
`c_farad`	Yes	Capacitor value used in farads.
`period_s`	Yes	Total period in seconds (astable only, null for monostable).
`c_display`	Yes	Human-readable capacitor value string (e.g. '100 nF', '4.7 µF').
`time_low_s`	Yes	Output LOW duration in seconds (astable only, null for monostable).
`time_high_s`	Yes	Output HIGH duration in seconds. In astable this is the charge time; in monostable this is the pulse width.
`frequency_hz`	Yes	Output frequency in Hz (astable only, null for monostable).
`duty_cycle_pct`	Yes	Duty cycle as a percentage (astable only, null for monostable). Always > 50% for standard 555.

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 carries full burden. It discloses the always >50% duty cycle limitation in astable mode and mentions the diode workaround. It also implies the tool is a calculator with no destructive side effects. Output parameters are listed (frequency, period, duty cycle, durations), though the exact return structure is covered by the output schema.

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 well-structured paragraph that fronts the purpose, then provides formulas, usage tips, and chaining suggestions. Every sentence adds value without redundancy. Slightly longer than necessary but still efficient.

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 modes, formulas, duty cycle behavior, and integration with sibling tools. For a moderate-complexity calculator, this is fully sufficient.

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

Parameters5/5

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

Schema coverage is 100%, baseline 3. Description adds significant meaning beyond the schema by explaining the formulas (e.g., f = 1.44 / ((R1 + 2·R2) · C)), clarifying that R2 is astable-only, noting typical capacitor ranges and scientific notation usage. This greatly aids correct parameter invocation.

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?

Description uses specific verb 'calculates' and explicitly names the IC (NE555/LM555) and both modes (astable, monostable). It distinguishes itself from sibling tools by mentioning chaining from ohms_law and resistor_color_code.

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 clear guidance on when to use each mode (astable for continuous square wave, monostable for one-shot pulse) and includes a critical note about duty cycle limitation (>50% for astable) with a workaround (diode across R2). Also suggests chaining to other tools for extended functionality, though it doesn't explicitly state when not to use this tool over others.

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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