Agentic Mermaid

Agentic Mermaid, a new open-source tool, combines a Mermaid parser, deterministic renderer, style system, and verification loop to let AI agents create, style, and export diagrams while keeping the Mermaid source reviewable. It offers built-in styles, palette themes, and multiple output formats (SVG, PNG, ASCII, Unicode, layout JSON), with a library, CLI, and MCP server for agent-native control. The tool includes verifyMermaid for structural and geometric warnings, and supports one-request, three-channel operation via library, CLI, or MCP.

Agentic Mermaid combines a Mermaid parser, deterministic renderer, style system, and verification loop. Your agent can create a diagram, apply a style and brand palette, export the artifact you need, and keep the Mermaid source reviewable for the next edit. Beautiful renders Built-in styles cover docs, decks, reports, terminals, sketches, and blueprints. Palette themes and custom JSON styles encode brand colors, typography, strokes, fills, and page backdrops. SVG and PNG serve pages and decks; ASCII, Unicode, and layout JSON serve review tools and agents. Agent-native control Typed parse and mutate helpers make Mermaid source the durable interface. verifyMermaid reports structural, geometric, and lint warnings with stable codes. start.md, CLI, library, and MCP surfaces give agents one tested operating path. The result is source you can review, renders you can ship, and an edit loop your agent can repeat. One request, three channels Ask the agent to make the diagram, set style and palette, verify the source, and return the render path through whichever channel it already has. Library js import { parseRegisteredMermaid, asFlowchart, mutate, verifyMermaid, serializeMermaid } from 'agentic-mermaid/agent' const flow = asFlowchart parseRegisteredMermaid source .value const r = mutate flow, { kind: 'add edge', from: 'API', to: 'Cache' } if verifyMermaid r.value .ok throw new Error 'edit left structural warnings' const next = serializeMermaid r.value CLI bash $ am mutate diagram.mmd --op '{"kind":"add edge","from":"API","to":"Cache"}' applies the op, verifies, emits source $ am verify diagram.mmd --json tiered warnings, stable codes $ am render diagram.mmd --format unicode same layout, in the terminal MCP // MCP Code Mode: the hosted MCP at https://agentic-mermaid.dev/mcp, or a self-hosted server. // The whole loop runs in one execute code call; the SDK is bound as mermaid . execute const source = 'flowchart LR\n UI Web app -- API\n API -- DB Postgres ' const flow = mermaid.asFlowchart mermaid.parseRegisteredMermaid source .value const r = mermaid.mutate flow, { kind: 'add edge', from: 'API', to: 'Cache' } const v = mermaid.verifyMermaid r.value return v.ok ? { source: mermaid.serializeMermaid r.value } : { error: 'verify failed', warnings: v.warnings } In the cloned repo, am is bun run bin/am.ts; MCP wiring is in Getting started. Install locally in Getting started: clone, build, and wire the stdio MCP in two minutes. Style × palette One source, three styles Render SVG for docs, PNG for decks, ASCII or Unicode for review, and layout JSON when tooling needs coordinates. To change visual treatment, pass a style stack in render options; examples include watercolor,paper and ops-schematic,nord-light. Seed changes only sketch noise; node positions and edge routes stay fixed. Each card uses the same Mermaid source with different render options. Agents pass style, palette, and seed in the render call instead of rewriting labels or edges for visual changes. Sketch note For whiteboards, docs drafts, and agent working notes.