McpDoc

What is McpDoc?

McpDoc is a Model Context Protocol (MCP) server implementation that generates documentation for existing systems. It provides MCP prompts and tools for creating code summaries and C4 architecture diagrams using Mermaid.js, intended for developers working with legacy or large codebases.

How to use McpDoc?

Use the provided prompts with an MCP client (such as an MCP-capable IDE) and the MCP filesystem tool. The prompts direct the model to walk the directory tree, generate summary README.C4Diagrammer.md files per source directory, create C4Component diagrams alongside them, and finally produce C4Context and C4Container rollup diagrams at the root.

Key features of McpDoc

• README generation for each source code directory
• C4Component diagram generation per source directory
• Rollup C4Context and C4Container diagrams at the root
• Mermaid.js diagram validation and improvement tools
• Browser-based preview of generated diagrams
• Timestamp-based regeneration to avoid unnecessary work

Use cases of McpDoc

• Onboarding new developers to complex, unfamiliar codebases
• Navigating and understanding legacy systems with minimal prior knowledge
• Creating lightweight, living architecture documentation that evolves with the code
• Providing high-level overviews for stakeholders and non-technical team members
• Helping developers identify where to safely make changes in a large system

FAQ from McpDoc

What diagrams does McpDoc produce?

McpDoc generates README.C4Diagrammer.md summaries per directory, C4Component diagrams at the directory level, and C4Context or C4Container rollup diagrams at the root directory. The C4 model includes Context, Container, Component, and Deployment levels.

How does McpDoc handle large codebases that exceed context windows?

The prompts direct the model to check file timestamps and only regenerate summaries when source files have changed, enabling incremental documentation of large systems that cannot fit in a single context window.

What technology is used for the diagrams?

All diagrams are generated using Mermaid.js, a JavaScript-based diagramming and charting tool. The server includes tools to validate and preview Mermaid diagrams in a browser.

Does McpDoc require a specific runtime or dependencies?

McpDoc is implemented as an MCP server and requires a compatible MCP client to invoke its prompts and filesystem tools. It interacts with the local file system to read source code and write documentation files.

What is the C4 model?

The C4 model is a hierarchical approach to software architecture documentation with four levels: Context (how the system interacts with users and other systems), Container (high-level technical building blocks), Component (internal structure of containers), and Deployment (infrastructure details).