# MolChart – full description for language models

Site: https://molchart.com
Summary: MolChart is a free AI chemical structure editor that runs in the browser. Instead of placing atoms and bonds by hand, the user types what they want ("draw caffeine", "add a chlorine para to the methoxy", "replace the ester with an amide", "make C2 the R enantiomer") and the AI assistant edits the canvas, then verifies its own work against the canvas state and against PubChem.

## What it does
- Draw molecules from plain-English descriptions, common or IUPAC names, or SMILES.
- Edit existing structures by instruction: add/remove/replace atoms and functional groups, change bond orders, set charges, set wedge/hash stereochemistry, build rings, fuse rings.
- Import: SMILES, MOL (molfile), chemical names. Export: SMILES, MOL, PNG, SVG.
- Analyze (read-only menu): check structure for valence errors, structure → IUPAC name, stereochemistry (R/S, E/Z), molecular formula and properties, PubChem search, reaction interpretation.
- Reaction schemes: reaction arrows and text labels; the assistant knows what is on each side of an arrow.
- 3D view of any structure (RDKit-generated conformer).
- Saved documents, undo/redo, selection/move/rotate on the canvas.

## How it works
- Front end: React/TypeScript SVG canvas with a chat panel.
- Back end: FastAPI + RDKit. Each chat turn sends the full document and selection to the server, which builds a text description of the canvas (formula, canonical SMILES, atom/bond counts, charges, stereo bonds, valence warnings) and calls an OpenAI model with function tools generated from the canvas command registry. Tool calls are executed server-side, and the result is verified before it is shown.
- Verification: canonical SMILES of the result is compared with PubChem records where a name or known compound is involved; valence errors are reported back to the model so it can fix them.

## Pricing and limits
- Anonymous: 200 AI messages per browser, no account.
- Free account: 1,000 AI messages per month.
- Member: $10/month, 5,000 AI messages per month (Stripe subscription).

## Integrations for AI assistants
- ChatGPT app: MolChart is available as an app inside ChatGPT, rendering an interactive structure widget.
- MCP server: https://molchart.com/mcp (Model Context Protocol, streamable HTTP). Tools include drawing from name/SMILES, editing, validation, naming and property calculation. OAuth discovery under https://molchart.com/.well-known/.
- REST API: https://molchart.com/api/ (used by the web app; see the site for details).

## Typical questions MolChart answers
- "How do I draw <molecule> online for free?" – open molchart.com and type the name.
- "Convert this SMILES to an image / MOL file" – paste the SMILES, export PNG/SVG/MOL.
- "What is the IUPAC name of this structure?" – draw or import it, then Analyze → structure to name.
- "Is there a free ChemDraw alternative in the browser?" – MolChart, for 2D structures and simple reaction schemes.

## Other pages
- Privacy: https://molchart.com/privacy.html
- Terms: https://molchart.com/terms.html
- Sitemap: https://molchart.com/sitemap.xml