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circuitjs-mcp

by Suzu-Gears

circuitjs-mcp

An MCP server that lets AI agents operate the Falstad CircuitJS1 circuit simulator. Since it is a standard stdio MCP server, it works with any MCP-compatible client, including Claude Code, Codex CLI, Claude Desktop, and Cursor.

CircuitJS1 is the name of the HTML5/JavaScript version of Paul Falstad's circuit simulator—long familiar as the Java applet version, "Circuit Simulator Applet", and now running in the browser at falstad.com/circuit. When browsers discontinued Java applet support, Iain Sharp ported it to JavaScript with GWT; both the simulation engine and the circuit text format are shared with the applet version (circuit files from the applet era can be loaded as-is). The JavaScript interface this server uses is a feature added in CircuitJS1 and is not present in the applet version.

The server launches the compiled CircuitJS1 web app (bundled in webapp/, works offline) inside headless Chromium (Playwright) and exposes its JavaScript interface as MCP tools. Simulator state persists across tool calls, so you can interactively load a circuit → run it → take measurements → rewrite the circuit.

Setup

Prerequisites: Node.js 18 or later.

cd circuitjs-mcp
npm install          # postinstall で Playwright の Chromium も入ります
npm test             # スモークテスト(RC回路の過渡応答が理論値と一致するか等を検証)

If playwright install chromium is difficult in your environment, you can use an existing Chrome/Chromium:

export CIRCUITJS_CHROMIUM="/usr/bin/google-chrome"   # 例

Related MCP server: circuit-sim-mcp

Registering with MCP cliients

The launch command is the same for every client: node /絶対パス/circuitjs-mcp/server.mjs

Adding the environment variable CIRCUITJS_HEADFUL=1 displays the browser window, allowing a human to operate the same simulator directly alongside the agent (collaboration mode). All examples below include this variable; remove it if not needed.

Claude Code:

claude mcp add circuitjs -e CIRCUITJS_HEADFUL=1 -- node /絶対パス/circuitjs-mcp/server.mjs

Codex CLI:

codex mcp add circuitjs --env CIRCUITJS_HEADFUL=1 -- node /絶対パス/circuitjs-mcp/server.mjs

Clients that use config files (Claude Desktop's claude_desktop_config.json, Cursor's mcp.json, etc.):

{
  "mcpServers": {
    "circuitjs": {
      "command": "node",
      "args": ["/絶対パス/circuitjs-mcp/server.mjs"],
      "env": { "CIRCUITJS_HEADFUL": "1" }
    }
  }
}

The screenshot tool returns a PNG as MCP image content. On clients that do not support image display, save it to a file with the save_path argument instead.

List of tools

Tool

Description

circuit_load

Loads a circuit in Falstad text format (with validation). Returns the element list

circuit_state

Gets the time, voltage differences / currents / terminal voltages of all elements, and voltages of labeled nodes

run_transient

Runs for the specified simulation time and returns sampled time series from probes (node voltages, element current/voltage/power)

sim_control

run / stop / reset / status, maximum timestep setting, and value setting for external voltage sources

circuit_export

Exports the circuit in Falstad text or SVG

circuit_link

Generates a URL (?ctz= link) that opens the current circuit (or the specified text) directly on falstad.com. Use this when you want to inspect or edit it interactively in a browser

screenshot

PNG screenshot of the current schematic (returned as an image; can also be saved to a file)

eval_js

Escape hatch for operations not covered above. Executes arbitrary JS on the sim object

Usage examples (sample instructions for an agent)

  • "Build an RC low-pass filter with 1kΩ and 1µF, feed it a 1kHz square wave, and capture the output waveform for 5ms."

  • "Load this circuit (paste the text) and list the power dissipation of each resistor."

  • "Show me a screenshot of the circuit."

To measure a point of interest, place a labeled node (element type 207, e.g. 207 336 128 400 128 4 out); the voltage can then be read with a {"node":"out"} probe or via circuit_state's nodes. For per-element current and voltage, use the index returned by circuit_load / circuit_state.

Direct use from scripts

If you want to call the tools from a script without going through an MCP client, use drive.mjs. It starts the server as a child process, executes the JSON files placed in the command directory (cmd-1.json, cmd-2.json, ...) in order, and writes the results to res-N.json:

node drive.mjs /tmp/cjs-commands
# 別プロセスから: echo '{"tool":"circuit_state","args":{}}' > /tmp/cjs-commands/cmd-1.json

Write files under a temporary name and then rename them into place (to avoid reading them mid-write).

Environment variables

Variable

Description

CIRCUITJS_CHROMIUM

Path to the Chrome/Chromium executable to use (default: Playwright-managed Chromium; falls back to system Chrome if it fails)

CIRCUITJS_URL

URL of a CircuitJS1 web app to load instead of the bundled one (e.g., https://www.falstad.com/circuit/circuitjs.html)

IRCUITJS_HEADFUL

Set to 1 to show the browser window (for debugging)

Limitations

  • The simulation speed of run_transient depends on the simulation speed setting in the circuit's $ line and on the CPU. If it takes too long in wall-clock time, it is cut off by wallTimeoutMs and partial data is returned (distinguishable via the reason field).

  • "Editing" a circuit basically means rewriting the Falstad text and calling circuit_load again (importing resets the time).

  • Transient analysis only (CircuitJS1 itself does not have AC small-signal analysis, etc.). Frequency response can be obtained by sweeping the frequency and repeating run_transient.

License

This entire repository is provided under GPL-2.0-or-later (COPYING.txt).

  • CircuitJS1 is GPLv2+ software by Paul Falstad / Iain Sharp. webapp/ is its compiled build (unmodified); the corresponding source code is available at pfalstad/circuitjs1 (the original) and the pages branch of code4fukui/circuitjs1 (where this build was obtained).

  • Server code (server.mjs, drive.mjs, test-client.mjs) © 2026 Suzu(涼鈴), GPL-2.0-or-later.

Available Tools

8 tools
circuit_exportExport circuitB

Export the current circuit as Falstad text format, or as an SVG drawing of the schematic.

ParametersJSON Schema
NameRequiredDescriptionDefault
formatNoDefault "text".

TDQS

B3.4/5.0
Behavior3/5

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

With no annotations, the description must carry the behavioral context. It clearly indicates the tool produces either Falstad text or SVG, but it does not disclose whether the export returns content directly, creates a file, or has any side effects. Some useful behavior is stated, but meaningful context is missing.

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 a single, well-structured sentence that conveys the tool's purpose and its two output formats without redundancy. Every word contributes meaning.

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

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The tool is simple, with one optional parameter, so extensive documentation is not required. However, since there is no output schema, the description does not clarify what the tool returns or how the exported content is delivered, leaving some ambiguity for an agent.

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?

While the schema already documents the 'format' enum and default, the description enriches the enum values by explaining that 'text' means Falstad text format and 'svg' means a drawing of the schematic. This adds value beyond the bare parameter name and enum list.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description names a specific verb ('Export'), the resource ('the current circuit'), and two concrete output formats ('Falstad text format' or 'SVG drawing'). It is clear and informative, though it does not explicitly distinguish itself from sibling tools like screenshot or circuit_link.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

There is no guidance about when to choose this tool over alternatives such as screenshot or circuit_link. The description states what it does but not in what situations it is preferred, nor what it is not for.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

circuit_loadLoad circuitA

Replace the current circuit with the given circuit definition in Falstad CircuitJS1 text format (the same format produced by File > Export as Text, starting with a "$" line). Resets simulation time to 0. Returns the list of parsed elements so you can verify the circuit and note element indices for probing. The simulator keeps state between tool calls.

ParametersJSON Schema
NameRequiredDescriptionDefault
runNoStart the simulation running after load (default false).
textYesCircuit in Falstad text format. First line is the "$" options line: `$ flags timestep simSpeed currentSpeed voltageRange powerScale minTimestep`. A reasonable default: "$ 1 0.000005 10.20027730826997 50 5 50 5e-11". Coordinates are grid-snapped multiples of 16.

TDQS

A4.3/5.0
Behavior4/5

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

No annotations are provided, so the description carries the full burden. It discloses key side effects: replacing the current circuit, resetting simulation time to 0, keeping simulator state across calls, and returning parsed elements for verification. This goes beyond the bare schema and gives the agent useful behavioral expectations.

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 purposeful sentences cover action, input format, side effects, return value, and state persistence. The core operation is front-loaded, and there is no filler or repetition.

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?

For a moderately simple load tool with no output schema, the description covers the required input format, reset behavior, return value, and cross-call statefulness. Combined with a fully described schema, an agent has enough to call it correctly and interpret the result.

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 description coverage is 100%, and the schema already explains the text format, the '$' line, reasonable defaults, and the run boolean. The tool description adds no parameter-specific meaning beyond noting the returned element list, so the baseline score of 3 applies.

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?

States the operation (replace), the exact resource (current circuit), the input format (Falstad CircuitJS1 text starting with a '$' line), and the return value. This stands apart from siblings such as circuit_export and circuit_state, so an agent can select it correctly.

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?

Clear that this tool is for installing a new circuit definition and that simulator state persists across calls, implying use at circuit-setup/load time. It does not explicitly name alternatives or say when not to use it, but no sibling has an overlapping function, so the gap is small.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

circuit_stateRead circuit stateA

Read the current simulation state: time, running flag, timestep, and every element with its voltage difference, current, post voltages and info string. Use the element index values with run_transient probes. Optionally pass node names (of labeled nodes, e.g. from "207 ..." labeled-node elements) to read their voltages.

ParametersJSON Schema
NameRequiredDescriptionDefault
nodesNoLabeled node names to read voltages for.

TDQS

A4.2/5.0
Behavior4/5

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

No annotations are provided, so the description carries the full behavioral burden. It clearly frames the operation as a non-mutating read and lists what will be reported. It does not disclose potential edge cases such as behavior when the simulation is not running or the possibility of very large output, but it is generally transparent for a read-only state inspection tool.

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, each serving a distinct purpose: stating the primary behavior, linking to run_transient usage, and explaining the optional parameter. There is no redundancy or filler, and the most important information is front-loaded.

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?

For a simple read tool with one optional parameter, the description covers the returned data, the source of valid node labels, and a cross-tool usage hint. Minor gaps such as output formatting, units, or error behavior are absent, but these are not critical for correctly invoking this 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?

The input schema has 100% description coverage, providing a baseline of 3. The description adds value beyond the schema by explaining that acceptable node names are labeled nodes and giving a concrete provenance example ('207 ...' labeled-node elements). It also clarifies the optional nature of the parameter.

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 states a clear read operation on the current simulation state and enumerates the specific data returned: time, running flag, timestep, and per-element voltage difference, current, post voltages, and info string. The verb 'read' and the explicit data inventory distinguish it from the write/control siblings in the context.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides a concrete usage hint: use returned element index values with run_transient probes. It also explains when to pass labeled node names. However, it does not explicitly state when to prefer circuit_state over siblings like circuit_load or sim_control, nor does it give any when-not-to-use guidance.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

eval_jsEvaluate JavaScript against the simulatorA

Advanced escape hatch: run arbitrary JavaScript inside the CircuitJS1 page. The code is the body of an async function receiving sim (the CircuitJS1 object, see https://www.falstad.com/circuit/doc/js-interface.html). Return a JSON-serializable value. Example: "return sim.getElements().filter(e => e.getType()==='ResistorElm').map(e => e.getCurrent())".

ParametersJSON Schema
NameRequiredDescriptionDefault
codeYes

TDQS

A4.3/5.0
Behavior4/5

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

With no annotations, the description carries the transparency burden. It clearly explains the execution model: code becomes an async function body, receives the `sim` object, and must return a JSON-serializable value. It does not spell out side effects or error behavior, but the phrase 'run arbitrary JavaScript' strongly implies mutating potential.

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?

Two sentences plus one example carry high information density with no filler. The core operational facts are front-loaded, and the example earns its place by clarifying the expected code shape.

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?

The description covers how to invoke the tool, what the code receives, the return contract, and links to the simulator's documented interface. It lacks explicit caveats about side effects or serialization failures, but given the tool's arbitrary-code nature and the provided example, an agent has enough to call it correctly.

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?

The single `code` parameter is fully elaborated despite 0% schema description coverage. The description defines what the code should look like, what context it receives, what it must return, and provides a practical example. This fully compensates for the schema's minimal parameter definition.

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 names a specific verb and resource: run arbitrary JavaScript inside the CircuitJS1 page. The 'advanced escape hatch' framing and concrete example clearly distinguish it from the sibling tools, which are more specialized operations.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Usage context is only implied by 'Advanced escape hatch,' suggesting it is a fallback when the standard tools cannot express the needed operation. It does not explicitly state when not to use it or name any sibling alternatives for common cases.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

run_transientRun transient simulationA

Run the simulation for a given amount of SIMULATED time while sampling probes, then stop. Returns time-series data {t, }. Probes: {"node":"name"} reads a labeled node voltage; {"element":i,"quantity":"current"|"voltageDiff"|"power"} reads element i (indices from circuit_state/circuit_load). Simulation speed is bounded by the circuit's sim-speed setting and CPU, so wall-clock time may differ from simulated time; the call aborts with partial data if wallTimeoutMs elapses first.

ParametersJSON Schema
NameRequiredDescriptionDefault
probesYes
secondsYesSimulated seconds to run, e.g. 0.01.
fromResetNoReset the circuit to t=0 first (default true).
maxSamplesNoMax samples to return (default 500).
wallTimeoutMsNoWall-clock abort, default 30000, max 120000.

TDQS

A4.2/5.0
Behavior4/5

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

With no annotations, the description must carry the behavioral burden, and it does: it explains that simulation stops after the target time, returns partial data if wallTimeoutMs is hit, and that wall-clock can differ from simulated time. It does not explicitly describe side effects on circuit state beyond what fromReset implies, but the disclosure is still substantial.

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 tightly structured: first sentence states the core operation, second defines the output and probe syntax, third explains timing behavior. Every sentence earns its place, and the key scoping constraint (SIMULATED time) is front-loaded.

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?

For a tool with five parameters, no annotations, and no output schema, the description is largely complete: it covers probe semantics, return shape, timeout behavior, and the sim-speed relationship. It could add a bit more detail about the exact output format or default reset behavior, but these are at least hinted at or covered by the schema.

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 80%, so some parameter meaning is already provided. The description adds real value by defining probe syntax and semantics: node probes read labeled voltage, element probes read current/voltageDiff/power with indices from circuit_state/circuit_load. This goes beyond the bare schema and compensates for the harder-to-infer parameters.

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 states a specific action ('Run the simulation'), the resource (a transient simulation), and the core distinguishing scope (simulated time with probe sampling). It also identifies the return type as time-series data, so it is clear how this tool differs from siblings like circuit_load or circuit_state.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description gives useful context, including how probe indices relate to circuit_state/circuit_load and how sim-speed affects wall-clock time. However, it never explicitly states when to prefer this tool over an alternative or what would be a better tool for a different task, such as sim_control.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

screenshotScreenshot the schematicA

Take a PNG screenshot of the circuit as currently drawn (including scope traces if the circuit defines scopes). Returns the image; optionally also saves it to save_path.

ParametersJSON Schema
NameRequiredDescriptionDefault
save_pathNoAbsolute file path to also save the PNG to.

TDQS

A4.1/5.0
Behavior4/5

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

With no annotations, the description carries the full behavioral disclosure burden. It states that the tool returns a PNG image, optionally saves it to save_path, and includes scope traces only when scopes are defined. It does not mention file-overwrite behavior, but the core side effects are transparent.

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 a single front-loaded sentence that conveys the primary action, the return value, the inclusion condition, and the optional parameter without redundancy. Every clause contributes useful information.

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?

For a simple one-optional-parameter capture tool with no output schema, the description fully explains what is returned and the only optional side effect. An agent has enough information to invoke the tool correctly.

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 description coverage is 100%, and the description only restates what the schema already says about save_path ('optionally also saves it to save_path'). No additional parameter meaning is added beyond the schema's explicit 'Absolute file path to also save the PNG to.'

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 opens with a specific verb and resource ('Take a PNG screenshot of the circuit as currently drawn') and clarifies the included content ('including scope traces if the circuit defines scopes'). This clearly distinguishes the tool from siblings like circuit_export and circuit_load.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies use for capturing the current visual circuit state and notes when scope traces are included, but it never explicitly states when to use this tool versus alternatives such as circuit_export. Usage context is present only by implication.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

sim_controlControl simulationB

Start/stop/reset the simulation, set the max timestep, or set the voltage of an external voltage source (an "Extern voltage" element, type ExtVoltageElm, addressed by its name). "reset" reloads the current circuit, zeroing time and all state.

ParametersJSON Schema
NameRequiredDescriptionDefault
actionNo
extVoltageNo
maxTimeStepNoSeconds, e.g. 5e-6.

TDQS

B3.1/5.0
Behavior3/5

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

With no annotations provided, the description carries the behavioral disclosure burden. It usefully discloses reset semantics ('reloads the current circuit, zeroing time and all state'), but does not explain side effects of run/stop, whether operations block, or what status returns.

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?

The description is a single, front-loaded sentence that conveys the primary actions efficiently. The parenthetical detail about external voltage elements is somewhat dense but adds necessary precision without redundancy.

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

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The description omits the 'status' action entirely even though it appears in the schema enum. It also provides no return-value information, no constraints on combining parameters, and no mention of prerequisites, which is significant for a control tool with no output schema and no annotations.

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 description coverage is low at 33%, and the description partially compensates by explaining extVoltage as an external voltage source element addressed by name. However, the action enum values have no accompanying behavioral descriptions, and maxTimeStep relies on the schema's unit example.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly identifies the tool's purpose: starting, stopping, resetting the simulation, setting max timestep, and setting external voltage source values. It uses specific verbs and a named resource, though it does not explicitly differentiate itself from siblings like run_transient.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides no explicit guidance on when to use this tool versus alternatives such as run_transient. The action enum implies some usage, but there are no stated conditions, exclusions, or selection criteria.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Tool Schema Changelog

Recent tool additions, removals, and schema changes observed during successful MCP inspections.

  1. 8 tool updatesv1.0.0
    • First observedcircuit_export
    • First observedcircuit_link
    • First observedcircuit_load
    • First observedcircuit_state
    • First observedeval_js
    • First observedrun_transient
    • First observedscreenshot
    • First observedsim_control

TDQS

A3.9/5.0

Scored across 8 tools

Disambiguation5/5

Each tool has a clear, distinct role: loading/exporting circuits, reading state, controlling simulation, running transient probes, taking screenshots, generating links, and escaping to JS. circuit_state and run_transient are separated clearly as snapshot vs. time-series sampling.

Naming Consistency3/5

Four tools use the circuit_ prefix, while sim_control, run_transient, screenshot, and eval_js follow different patterns. The names are still readable, but the convention is not uniformly applied across the server.

Tool Count5/5

Eight tools is a well-scoped count for a circuit simulator server. Each tool maps to a meaningful user need without redundancy or bloat.

Completeness5/5

The set covers the full simulation workflow: load, export, inspect, control, run transient analysis, capture output, and share. eval_js provides an escape hatch for anything not explicitly exposed, leaving no obvious dead ends.

Maintenance

ActivityMaintained
ResponsivenessNo issues

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