Indicator packages

Every indicator on a chart, and every indicator value the REST API answers, comes from an indicator package: a small ZIP with a manifest and a JavaScript calculation. The app ships eight (Moving average, RSI, Bollinger, MACD, AO, AC, Alligator and EO); you can install your own from the Indicators page. This page is the format, for writing a package by hand. To convert an MT4 indicator, see Converting an MT4 indicator.

The app computes a package's values in the server, in a sandbox, and serves the same values to every chart and to REST. A package sees only its bars and its parameters, so its output depends on nothing else.

The files

A package is exactly four files, at the root of a ZIP:

File	What it holds
`manifest.json`	What the package is: its ID, version, parameters, outputs and drawing.
`calculate.js`	The calculation.
`README.md`	What it computes, for the Indicators page.
`LICENSE`	Its licence text.

The ZIP is at most 2 MiB, and each file at most 256 KB of UTF-8 text.
Nothing else may be in the ZIP: no folders, other files, links, encryption or ZIP64. Use a plain ZIP (deflate or stored).
npm run indicator-package -- <folder> builds the ZIP from a folder with the four files (see Installing).

manifest.json

Format apiVersion 1, the legacy QuoteBridge server's, so its packages load unchanged. Any field not listed here is refused.

Field	Required	Value
`apiVersion`	yes	`1`.
`id`	yes	Lowercase letters, digits, dots or hyphens, starting with a letter, up to 100. Use a prefix of your own (`acme.momentum`); the bundled packages' IDs start with `quotebridge.`.
`version`	yes	`major.minor.patch`, such as `1.2.0`. See Versions.
`name`	yes	The name on menus and in the legend, up to 80 characters.
`description`	yes	One or two sentences, up to 2000 characters.
`license`	yes	The licence's name, such as `MIT`, up to 100 characters. The text goes in `LICENSE`.
`entry`	yes	`"calculate.js"`.
`inputs`	yes	Exactly one input, the source (below).
`parameters`	yes	Up to 12 parameters (below); `[]` for none.
`outputs`	yes	1 to 8 outputs (below).
`closedBarsOnly`	no	`true`: the package never gets the bar still forming. Its values appear as each bar closes.
`levels`	no	Up to 8 numbers, drawn as dashed horizontal lines on the package's pane (RSI's `[30, 70]`).
`range`	no	`{ "min": 0, "max": 100 }`: a fixed scale for the package's pane. Its values then read with 2 decimals.

levels and range need outputs placed in a pane.

The input

{ "id": "source", "label": "Close", "kind": "numeric", "alignment": "exact", "field": "close", "history": { "bars": 50 } }

id is "source", kind "numeric" and alignment "exact"; label names the price (up to 80 characters).
field is close (the default) or median, which is (high + low) / 2. These are the only two prices a package gets.
history is the warm-up: how many bars the package needs before the first value it shows. The app hands it that many bars before the first bar on the chart (or the first REST asks for), so the first value shown is as correct as the last. It is either:
- { "bars": 50 }: a fixed number, 1 to 5000;
- { "parameter": "period", "extra": 499 }: an integer parameter (with min 1 or more) plus some bars, 5000 at most with the parameter at its maximum.
An average that starts from its first value (an EMA, Wilder's smoothing) needs generous warm-up to settle: the bundled RSI and MACD declare their period plus 499.

Parameters

A number parameter:

{ "id": "fast", "label": "Fast EMA", "type": "integer", "default": 12, "min": 1, "max": 500, "lessThan": "slow" }

id: starts with a lowercase letter, then letters, digits or _ (jawShift is fine), up to 40.
label: what the settings form shows.
type: integer (whole numbers) or number.
default within min and max. The settings form and REST refuse values outside them.
lessThan (optional): another number parameter's ID. Its value must stay below that one's, by default too (MACD's fast period below its slow one).

A choice parameter, a list of labelled values:

{ "id": "type", "label": "Type", "type": "choice", "default": "simple", "choices": [{ "value": "simple", "label": "Simple" }, { "value": "exponential", "label": "Exponential" }] }

1 to 16 choices. A value follows the output ID rule below; calculate gets the value, the form shows the label.

Outputs

{ "id": "macd", "label": "MACD", "kind": "numeric", "render": "histogram", "placement": "pane", "color": "#a3afc2", "unit": { "input": "source" } }

id: lowercase letters, digits or _, starting with a letter, up to 40.
label: what the legend shows. A package with one output is read by its name instead.
kind: "numeric". unit: { "input": "source" }.
render: line or histogram.
placement: overlay (on the price) or pane (a pane of its own under the price). Every output of a package has the same placement.
color: #rrggbb. Required, but the chart chooses the colours (see What the chart draws).
palette (histograms only, optional): up to 16 style keys, each named like an output ID, with a #rrggbb colour: { "rising": "#26a69a", "falling": "#ef5350" }. A point picks one with its styleKey.
lineWidth (1 to 4) and lineStyle (solid, dashed, dotted), lines only, optional: accepted for legacy packages; the chart draws every line at its own width, solid.

calculate.js

The file sets exports.calculate, a function that takes the bars and the parameters and returns every output's values:

exports.calculate = function ({ inputs, parameters, timeline, asOf }) {
  const points = inputs.source.points; // [{ time, value }], oldest first
  return { outputs: { line: timeline.map((time, i) => ({ time, value: points[i].value })) } };
};

What it gets:

inputs.source.points: one { time, value } per bar, oldest first. time is the bar's open time in UTC seconds; value is its close, or its median price.
timeline: the bars' times, the same as points.map((p) => p.time).
parameters: every parameter by ID, already checked against the manifest (in range, lessThan kept, a choice one of its values).
asOf: the last bar's time.

The bars are the warm-up, then the bars a chart has loaded (or REST asked for). The last one is the bar still forming, unless the package is closedBarsOnly. The package is called again, over every bar, whenever they change: when a chart loads older bars, and at most once a second while the forming bar moves. Each call starts from nothing, so compute everything from points.

What it returns: { outputs: { <output id>: [points] } }, with every output the manifest lists and no other. Each point is { time, value, styleKey? }:

time is one of the bars' times, in increasing order, at most one point per bar. Bars without a point have no value.
value is a finite number, or null where the output has no value (during its warm-up, for instance). 0 is a real value.
styleKey (optional) is one of the output's palette keys.

Anything else (a missing or extra output, a time out of order, NaN or Infinity, an unknown style key) is invalid output, and the calculation fails.

The sandbox

calculate.js runs in QuickJS, a separate JavaScript engine, on a worker thread of its own. Its output can depend only on its bars and its parameters:

500 ms per call, a 32 MiB heap, and a 1 MiB stack.
At most 50,000 bars in one call.
Standard JavaScript (Math, JSON, arrays, typed arrays, Map, …), without Date and Math.random.
No require or import, no network, no files, no timers and no console. The file is one script: bundle anything it needs into it.

A call that runs too long, runs out of memory, throws or returns invalid output fails. The indicator's legend row then reads "Failed" with the reason, and the chart keeps its last good values, greyed. REST answers 422 with the reason.

What the chart draws

A line joins its values. A histogram draws a bar from zero for each value, over a zero line.
overlay outputs are drawn on the price. pane outputs get a pane of their own, one per indicator, which the trader can resize.
levels are dashed lines on the pane, and range fixes its scale. A pane with a histogram already has a solid zero line, so it needs no level at 0.
Values read in the market's digits, or with 2 decimals on a pane with a range.

Packages don't choose their colours; the chart does, from the trader's theme, so that indicators never look like price direction:

Each line, and each histogram of one colour, takes the series palette's least-used colour (gold, azure, violet, slate).
A histogram whose palette has the keys rising and falling draws those bars in the chart's Uptick and Downtick colours, as on the candles. Give each of its points one of the two keys.
Other palette keys are kept in the data (REST answers them in styles) but are drawn in the output's one colour.
The trader can change any output's colour, or swap rising and falling, from the legend.

Arrows, markers, fills between lines, text, and values drawn past the last bar are not supported.

Installing

Build the ZIP. In a working copy of this repository, put the four files in a folder and run npm run indicator-package -- <folder>. It makes the same checks as Install, runs the package once on test bars, and writes build/<id>-<version>.zip. Any ZIP tool works too, with the four files at the ZIP's root.
In the app window, open Indicators in the rail and click Install package…, or drop the ZIP on the page.
The app checks the ZIP, runs the package on test bars with its defaults, and shows its manifest, README and licence. Nothing is installed yet.
Click Install. A new package is enabled and appears in the chart's Indicators menu, after the bundled ones; a new version of an installed one keeps its switch, enabled or not.

A refused ZIP says why (a bad manifest, a missing file, too big, a failed trial run). On the same page you can disable a package (it leaves the Indicators menu; charts using it read "Not available" until it is enabled again) and delete an installed one. Bundled packages can be disabled but not deleted.

Only the app window can install, enable, disable or delete packages. A remote browser sees the Indicators page read-only, and REST has no way to change packages.

Versions

A package is its id plus its version, and the app keeps one version of each id.

Installing a newer version replaces the installed one. The preview shows the old and new versions and the parameters added or removed. Charts keep the values of parameters that still exist; new ones take their defaults.
Installing an older version asks a second time.
The same version with different files is refused: a version always means the same four files (the app keeps a SHA-256 over them). Change the version with any change.
A bundled package's ID (quotebridge.ma, quotebridge.rsi, quotebridge.bollinger, quotebridge.macd, quotebridge.ao, quotebridge.ac, quotebridge.alligator, quotebridge.eo) can't be used: those packages update only with the app.

Converting an MT4 indicator

This repository has a skill for coding agents, mt4-indicator-to-package (in skills/), that converts an .mq4 indicator into a package: it checks the indicator can be converted, maps its buffers, writes the four files and tests against values worked out by hand, then checks the result against values you copy from MT4's Data Window. Ask your agent to convert the indicator and give it the .mq4 file.

Example

A histogram in its own pane of how far the close moved over the last period bars, coloured rising or falling against the bar before.

manifest.json

{
  "apiVersion": 1,
  "id": "example.change",
  "version": "1.0.0",
  "name": "Close change",
  "description": "The close less the close a number of bars before, as bars rising or falling against the bar before.",
  "license": "MIT",
  "entry": "calculate.js",
  "inputs": [{ "id": "source", "label": "Close", "kind": "numeric", "alignment": "exact", "field": "close", "history": { "parameter": "period", "extra": 1 } }],
  "parameters": [{ "id": "period", "label": "Period", "type": "integer", "default": 10, "min": 1, "max": 500 }],
  "outputs": [
    {
      "id": "change",
      "label": "Change",
      "kind": "numeric",
      "render": "histogram",
      "placement": "pane",
      "color": "#26a69a",
      "palette": { "rising": "#26a69a", "falling": "#ef5350" },
      "unit": { "input": "source" }
    }
  ]
}

calculate.js

// The close less the close `period` bars before; null until that bar exists. Rising when higher than the bar
// before's value (the first value: when above zero), falling otherwise.
exports.calculate = function ({ inputs, parameters, timeline }) {
  const closes = inputs.source.points.map((point) => point.value);
  const n = parameters.period;
  let previous = 0;
  const change = timeline.map((time, i) => {
    if (i < n) return { time, value: null };
    const value = closes[i] - closes[i - n];
    const point = { time, value, styleKey: value > previous ? "rising" : "falling" };
    previous = value;
    return point;
  });
  return { outputs: { change } };
};

README.md

# Close change

The close less the close `period` bars before, as bars in their own pane: rising when higher than the bar before,
falling otherwise.

LICENSE

MIT License

Copyright (c) 2026 Example

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated
documentation files (the "Software"), to deal in the Software without restriction, including without limitation the
rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit
persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the
Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Worked by hand

With period 2 and the closes 1, 2, 4, 3, 3, 6:

Bar	Close	Change	Style
1	1	null
2	2	null
3	4	4 − 1 = 3	rising (above zero)
4	3	3 − 2 = 1	falling
5	3	3 − 4 = −1	falling
6	6	6 − 3 = 3	rising

This repository's tests install this example and check these values (tests/indicator-packages-doc.test.ts).

This page is docs/indicator-packages.md in the app's repository.View on GitHub