RFCXML MCP Server

日本語版 README

A Model Context Protocol (MCP) server for structured understanding of RFC documents.

Purpose

Unlike existing text-based RFC MCP servers, this server leverages the semantic structure of RFCXML to enable:

• Normative requirements extraction (MUST/SHOULD/MAY) with structured output
• RFC dependency graph construction
• Definition scope management
• Implementation checklist generation

Architecture

┌─────────────────────────┐
│  Markdown / PDF         │  Display & Sharing
├─────────────────────────┤
│  Translation            │  Explanation & Verification
├─────────────────────────┤
│  RFCXML MCP             │  Common Understanding for AI & Humans
├─────────────────────────┤
│  RFCXML                 │  Single Source of Truth
└─────────────────────────┘

Comparison with Existing MCPs

| Feature | Existing mcp-rfc | RFCXML MCP | | ------------------------------- | ---------------- | -------------------- | | RFC text retrieval | ✅ | ✅ | | Section extraction | ✅ (text-based) | ✅ (structure-based) | | MUST/SHOULD/MAY extraction | ❌ | ✅ | | Condition/exception structuring | ❌ | ✅ | | RFC dependency graph | ❌ | ✅ | | Definition scope management | ❌ | ✅ | | Implementation checklist | ❌ | ✅ |

Quick Start

Using with Claude Desktop / Claude Code

Add the following to your MCP configuration file:

{
  "mcpServers": {
    "rfcxml": {
      "command": "npx",
      "args": ["-y", "@shuji-bonji/rfcxml-mcp"]
    }
  }
}

Configuration file locations:

• Claude Desktop (macOS): ~/Library/Application Support/Claude/claude_desktop_config.json
• Claude Desktop (Windows): %APPDATA%\Claude\claude_desktop_config.json
• Claude Code: .claude/settings.json or use claude settings command

Installation (Optional)

For global installation:

npm install -g @shuji-bonji/rfcxml-mcp

# MCP configuration
{
  "mcpServers": {
    "rfcxml": {
      "command": "rfcxml-mcp"
    }
  }
}

Available Tools

Phase 1: Basic Structure

• get_rfc_structure - Get section hierarchy and metadata
• get_requirements - Extract normative requirements (MUST/SHOULD/MAY) with structure
• get_definitions - Get term definitions and their scope

Phase 2: Relationships

• get_rfc_dependencies - Get referenced RFCs (normative/informative)
• get_related_sections - Get related sections within the same RFC

Phase 3: Verification Support

• validate_statement - Verify if a statement complies with RFC requirements
• generate_checklist - Generate implementation checklist

Legacy RFC Support

RFCs published after RFC 8650 (December 2019) are available in official RFCXML v3 format. Earlier RFCs may not have XML available.

This server includes automatic fallback functionality - when XML is unavailable, it parses the text format instead.

Source Information

All responses include source information:

{
  "rfc": 6455,
  "sections": [...],
  "_source": "text",
  "_sourceNote": "⚠️ Parsed from text format. Accuracy may be lower."
}

| _source | Description | | --------- | ---------------------------------- | | xml | Parsed from RFCXML (high accuracy) | | text | Parsed from text (medium accuracy) |

Compatibility

| RFC | Format | Notes | | --------------- | ------ | -------------------------- | | RFC 8650+ | XML | Official RFCXML v3 support | | Before RFC 8650 | Text | Automatic fallback |

Output Samples

get_rfc_structure - Get RFC Structure

{
  "metadata": {
    "title": "Transmission Control Protocol (TCP)",
    "docName": "draft-ietf-tcpm-rfc793bis-28",
    "number": 9293
  },
  "sections": [
    {
      "number": "section-1",
      "title": "Purpose and Scope"
    },
    {
      "number": "section-3",
      "title": "Functional Specification",
      "subsections": [
        { "number": "section-3.1", "title": "Header Format" },
        {
          "number": "section-3.5",
          "title": "Establishing a Connection",
          "subsections": [
            { "number": "section-3.5.1", "title": "Half-Open Connections and Other Anomalies" },
            { "number": "section-3.5.2", "title": "Reset Generation" }
          ]
        }
      ]
    }
  ],
  "referenceCount": { "normative": 15, "informative": 85 },
  "_source": "xml"
}

get_requirements - Extract Normative Requirements

{
  "rfc": 9293,
  "filter": { "level": "MUST" },
  "stats": { "total": 53, "byLevel": { "MUST": 53 } },
  "requirements": [
    {
      "id": "R-section-3.5-5",
      "level": "MUST",
      "text": "A TCP implementation support simultaneous open attempts (MUST-10).",
      "section": "section-3.5",
      "sectionTitle": "Establishing a Connection"
    },
    {
      "id": "R-section-3.7.1-9",
      "level": "MUST",
      "text": "TCP endpoints implement both sending and receiving the MSS Option (MUST-14).",
      "section": "section-3.7.1",
      "sectionTitle": "Maximum Segment Size Option"
    }
  ],
  "_source": "xml"
}

get_rfc_dependencies - Get RFC Dependencies

{
  "rfc": 9293,
  "normative": [
    { "rfcNumber": 791, "title": "Internet Protocol", "anchor": "RFC0791" },
    { "rfcNumber": 2119, "title": "Key words for use in RFCs to Indicate Requirement Levels" },
    { "rfcNumber": 5681, "title": "TCP Congestion Control" }
  ],
  "informative": [
    { "rfcNumber": 793, "title": "Transmission Control Protocol" },
    { "rfcNumber": 1122, "title": "Requirements for Internet Hosts - Communication Layers" }
  ],
  "_source": "xml"
}

generate_checklist - Generate Implementation Checklist

# RFC 9293 Implementation Checklist

**Transmission Control Protocol (TCP)**

Role: Client

## Required (MUST / REQUIRED / SHALL)

- [ ] A TCP implementation support simultaneous open attempts (MUST-10). (section-3.5)
- [ ] TCP endpoints implement both sending and receiving the MSS Option (MUST-14). (section-3.7.1)
- [ ] The RTO be computed according to the algorithm in, including Karn's algorithm (MUST-18). (section-3.8.1)

## Optional (MAY / OPTIONAL)

- [ ] Implementers include "keep-alives" in their TCP implementations (MAY-5). (section-3.8.4)

Text Fallback Output (Legacy RFCs)

{
  "metadata": {
    "title": "The WebSocket Protocol",
    "number": 6455
  },
  "sections": [
    { "number": "1", "title": "Introduction" },
    { "number": "5", "title": "Data Framing" }
  ],
  "_source": "text",
  "_sourceNote": "⚠️ Parsed from text format. Accuracy may be lower."
}

Examples

See the examples/ directory for complete checklist samples:

| RFC | Protocol | Source | | ----------------------------------------------------- | --------- | --------------- | | RFC 6455 | WebSocket | Text (fallback) | | RFC 9293 | TCP | RFCXML | | RFC 7540 | HTTP/2 | Text (fallback) |

Example prompt for Claude:

Generate an implementation checklist for RFC 9293 (TCP).

Internal Architecture

Module Structure

src/
├── index.ts                    # MCP server entry point
├── config.ts                   # Centralized configuration
├── constants.ts                # BCP 14 keyword definitions
├── services/
│   ├── rfc-fetcher.ts          # RFC fetching (parallel)
│   ├── rfcxml-parser.ts        # RFCXML parser
│   ├── rfc-text-parser.ts      # Text fallback parser
│   └── checklist-generator.ts  # Checklist generation service
├── tools/
│   ├── definitions.ts          # MCP tool definitions
│   └── handlers.ts             # Tool handlers
├── types/
│   └── index.ts                # Type definitions
└── utils/
    ├── cache.ts                # LRU cache
    ├── fetch.ts                # Parallel fetch utility
    ├── requirement-extractor.ts # Shared requirement extraction
    ├── section.ts              # Section search utilities
    ├── text.ts                 # Text processing utility
    └── validation.ts           # Input validation

RFC Fetch Optimization

Sends parallel requests to multiple sources (RFC Editor, IETF Tools, Datatracker) and uses the first successful response:

┌─────────────────┐
│  fetchRFCXML()  │
└────────┬────────┘
         │ Parallel requests
    ┌────┴────┬────────────┐
    ▼         ▼            ▼
┌────────┐ ┌────────┐ ┌────────┐
│RFC     │ │IETF    │ │Data-   │
│Editor  │ │Tools   │ │tracker │
└────┬───┘ └────┬───┘ └────┬───┘
     │          │          │
     └────┬─────┴──────────┘
          │ Promise.any (first success)
          ▼
    ┌───────────┐
    │ Successful│ → Cancel other requests via AbortController
    │ Response  │
    └───────────┘

Cache Strategy

LRU (Least Recently Used) cache with memory limits:

| Cache | Max Entries | Content | | -------------- | ----------- | ---------------- | | XML Cache | 20 | Raw RFCXML | | Text Cache | 20 | Raw text | | Metadata Cache | 100 | RFC metadata | | Parse Cache | 50 | Parsed structure |

Development

# Install dependencies
npm install

# Development mode
npm run dev

# Build
npm run build

# Test
npm test

# Lint
npm run lint

# Format
npm run format

License

MIT

Related Projects

• mjpitz/mcp-rfc - Text-based RFC MCP
• ietf-tools/RFCXML - RFCXML schema
• xml2rfc - IETF official tool