mermaid-chart-mcp

MermaidChart MCP Server

URL: https://mcp.mermaidchart.com/mcp Server: Mermaid Server v1.0.0 Date: 2026-06-26

Protocol

• Transport: HTTP POST with SSE (Server-Sent Events) responses
• Session: Created via initialize call, returns mcp-session-id header (UUID)
• Subsequent calls require Mcp-Session-Id header
• Accept header must be application/json, text/event-stream
• Server supports MCP protocol version 2024-11-05

Capabilities

• tools with listChanged support

Tools (17 total)

Mermaid Diagram Tools (5)

Tool	Access	Description
validate_and_render_mermaid_diagram	RO	Render Mermaid diagrams, returns image or error details
get_diagram_title	RO	Returns LLM prompts for title generation (see Notes)
get_diagram_summary	RO	Returns LLM prompts for summary generation (see Notes)
search_mermaid_icons	RO	Search AWS/Azure/GCP/FontAwesome icons for diagrams
get_mermaid_syntax_document	RO	Get full syntax docs for a specific diagram type

GitHub Tools (12)

Tool	Access	Description
list_repos	RO	List repos for user or org
list_mermaid_files	RO	Find .mmd files in a repo
read_mermaid_file	RO	Read a .mmd file from a repo
create_pr	RW	Create branch + commit + PR with file changes
push_file	RW	Create/update a single file on a branch
list_pulls	RO	List pull requests
list_branches	RO	List or resolve branch names
list_issues	RO	List issues
create_issue	RW	Create an issue
get_issue_comments	RO	Get comments on an issue
get_pull_comments	RO	Get PR comments (thread + inline)
list_tools	RO	List all available MCP servers and tools

Key Observations

• Every tool requires a clientName parameter (analytics tracking)
• GitHub tools require Github-Token header or GITHUB_TOKEN env var
• The server combines Mermaid diagram generation with GitHub repo operations
• The validate_and_render_mermaid_diagram tool is the primary rendering entry point
• Icon search supports AWS, Azure, GCP, and FontAwesome icon sets
• Server returns base64-encoded PNG images in responses
• Server provides preview/edit links for generated diagrams (shortened URLs)

Notes

• get_diagram_title and get_diagram_summary do not generate titles/summaries themselves. They return system/user prompts for the client LLM to perform the generation. The rendered response includes the diagram content + the prompts.
• validate_and_render_mermaid_diagram is the only Mermaid tool that performs actual work (rendering to PNG).
• Every tool requires a clientName parameter — used for analytics tracking by MermaidChart.
• GitHub tools require a Github-Token HTTP header (or GITHUB_TOKEN/GH_TOKEN env var on the server side).
• Server is a third-party public service at MermaidChart.com — not part of the satware AG/IPADP ecosystem.

Session Flow

1. Initialize session with initialize method
2. Send notifications/initialized notification
3. Use tools/list to discover available tools
4. Call tools with tools/call method

Example: Rendering a Flowchart

# Initialize session
RAW=$(curl -s -D - -X POST 'https://mcp.mermaidchart.com/mcp' \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"hermes","version":"1.0"}}}')

SESSION_ID=$(echo "$RAW" | grep -i '^mcp-session-id:' | sed 's/^mcp-session-id: *//;s/\r$//')

# Send initialized notification
curl -s -X POST 'https://mcp.mermaidchart.com/mcp' \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -H "Mcp-Session-Id: $SESSION_ID" \
  -d '{"jsonrpc":"2.0","method":"notifications/initialized"}' > /dev/null

# Render a diagram
curl -s -X POST 'https://mcp.mermaidchart.com/mcp' \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -H "Mcp-Session-Id: $SESSION_ID" \
  -d '{"jsonrpc":"2.0","id":2,"method":"tools/call","params":{"name":"validate_and_render_mermaid_diagram","arguments":{"prompt":"Simple flowchart showing a decision process","mermaidCode":"flowchart TD\n    A[Start] --> B{Is it working?}\n    B -->|Yes| C[Great!]\n    B -->|No| D[Fix it]\n    D --> B","diagramType":"flowchart","clientName":"hermes","useUrlShortener":true}}}'