★ Flagship AI capability
Describe Any Indicator — Your AI Builds It
Tell your AI agent what you want to see, and it invents the indicator from a formula and renders it live on your MyLinedChart chart. Your whole chart toolkit, driven by conversation.
What is a custom formula indicator?
MyLinedChart ships six built-in indicators — RSI, MACD, MA, EMA, BOLL, and VOL. A custom formula indicator is a seventh kind: one your AI agent invents on the spot from a math expression you describe in plain language, using MyLinedChart's MCP write channel (the propose_chart_changes tool — still one of nine MCP tools, not a new one).
Ask for "the gap between a 20 and 50 SMA," or "RSI smoothed by a 5-bar average," and your AI translates that into a formula, proposes it, and — once you confirm — it renders on your chart exactly like a built-in indicator.
How the sandbox keeps it safe
A custom formula is restricted math, never code. The formula can only reference your chart's own price data — open, high, low, close, and volume — through a fixed set of window functions (sma, ema, rsi, stdev, highest, lowest, and more) plus basic arithmetic. There is no eval, no scripting language, and no access to anything outside that list.
An unsupported or malformed formula is rejected before it's ever written to your chart, with a specific parse error — not silently ignored. The worst case if something is off is a wrong or mislabeled line on your chart. It is never code execution, never a trade, and never account access. Custom formula indicators also stay local to your device — they are never synced to the cloud.
Example formulas
Your AI handles the translation from plain language to formula. Here's what that looks like:
sma(close,20)-sma(close,50)close-ema(close,21)rsi(close,14)stdev(close,20)How to use it
- Download the MyLinedChart desktop app and enable the MCP server (see /mcp).
- Point an MCP-connected AI agent — Claude Code, Codex, or any MCP client — at it.
- Describe the indicator you want in plain language and ask your agent to add it to your chart.
- Confirm the proposed change when prompted — it renders on your chart immediately after.
Related Resources
Custom Formula Indicators FAQ
What can a custom formula indicator actually do?
It computes a restricted math expression over your chart's own OHLCV data — open, high, low, close, volume — using window functions like sma, ema, rsi, stdev, highest, and lowest, plus basic arithmetic. It renders as a line on your chart, same as a built-in indicator.
Can a custom formula indicator run arbitrary code?
No. There is no code execution — no eval, no scripting language, no access to anything outside the fixed set of price-data variables and window functions. An invalid or unsupported formula is rejected before it's ever written, with a specific parse error. Worst case if something is wrong, you get a mislabeled or incorrect line — never a trade, never account access, never a security risk.
Is my custom indicator synced to the cloud?
No. Custom formula indicators are local to your device. They render on your chart and are visible to your AI agent via the MCP server, but they are never uploaded to cloud sync.
How many built-in indicators does MyLinedChart have?
Six: RSI, MACD, MA, EMA, BOLL, and VOL. Custom formula indicators are additional to these six — invented on demand from a formula, not a fixed library.
Does this add a new MCP tool?
No. Custom formula indicators are a capability of the existing propose_chart_changes tool — one of MyLinedChart's nine MCP tools. No new tool was added.