# RFCXML MCP Server
[](https://www.npmjs.com/package/@shuji-bonji/rfcxml-mcp)
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[](https://opensource.org/licenses/MIT)
[](https://nodejs.org/)
[](https://claude.ai/code)
[日本語版 README](README.ja.md)
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:
```json
{
"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:
```bash
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:
```json
{
"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
```json
{
"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
```json
{
"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
```json
{
"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
```markdown
# 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)
```json
{
"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/](./examples/) directory for complete checklist samples:
| RFC | Protocol | Source |
| ----------------------------------------------------- | --------- | --------------- |
| [RFC 6455](./examples/rfc6455-websocket-checklist.md) | WebSocket | Text (fallback) |
| [RFC 9293](./examples/rfc9293-tcp-checklist.md) | TCP | RFCXML |
| [RFC 7540](./examples/rfc7540-http2-checklist.md) | 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
```bash
# 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](https://github.com/mjpitz/mcp-rfc) - Text-based RFC MCP
- [ietf-tools/RFCXML](https://github.com/ietf-tools/RFCXML) - RFCXML schema
- [xml2rfc](https://xml2rfc.ietf.org/) - IETF official tool
