Add MCP self-referencing docs and /docs endpoint

- Enhanced /.well-known/mcp.json to extract hostname from request headers (SNI/Host)
- Added self-referencing URLs that work with localhost, domains, and reverse proxies
- Documented all 5 API endpoints (random, raw, stream, cameras, health) as MCP tools
- Added /docs endpoint serving HTML documentation from skill.md
- Added /docs/skill.md for raw markdown access
- Added /docs/mcp.json as alias to /.well-known/mcp.json
- Created skill.md with comprehensive API documentation
- Markdown to HTML conversion happens at build time

Co-authored-by: Cursor <cursoragent@cursor.com>

skill.md

@@ -0,0 +1,189 @@
+# Camera TRNG API Skill Documentation
+
+This document describes how to use the Camera TRNG (True Random Number Generator) API as an MCP-compatible service.
+
+## Overview
+
+The Camera TRNG server provides quantum-based random number generation using thermal noise from a covered camera sensor. The API is accessible via HTTP and self-documents its capabilities through the `.well-known/mcp.json` endpoint.
+
+## Discovery
+
+The API can be discovered by fetching the MCP endpoint:
+
+```bash
+curl http://localhost:8787/.well-known/mcp.json
+```
+
+The response includes self-referencing URLs that use the request's hostname (from SNI/HTTP Host header), making it work correctly whether accessed via `localhost`, a domain name, or behind a reverse proxy.
+
+## API Endpoints
+
+### 1. Get Random Bytes (`/random`)
+
+Generate cryptographically secure random bytes from camera sensor entropy.
+
+**Parameters:**
+- `bytes` (integer, default: 32, max: 1048576): Number of random bytes to generate
+- `hex` (boolean, default: false): Return bytes as hexadecimal string instead of binary
+
+**Examples:**
+```bash
+# Get 32 bytes as binary
+curl "http://localhost:8787/random?bytes=32" -o random.bin
+
+# Get 64 bytes as hex string
+curl "http://localhost:8787/random?bytes=64&hex=true"
+
+# Get 1KB of random data
+curl "http://localhost:8787/random?bytes=1024" -o random.bin
+```
+
+### 2. Get Raw Data (`/raw`)
+
+Get raw LSB (least significant bit) data from camera sensor without cryptographic extraction. Useful for testing or custom post-processing.
+
+**Parameters:**
+- `bytes` (integer, default: 65536, max: 1048576): Number of raw bytes to extract
+
+**Example:**
+```bash
+curl "http://localhost:8787/raw?bytes=1024" -o raw.bin
+```
+
+### 3. Stream Random Bytes (`/stream`)
+
+Stream continuous random bytes using Server-Sent Events (SSE) format. Useful for high-throughput applications.
+
+**Parameters:**
+- `bytes` (integer, optional): Total bytes to stream (omit for unlimited)
+- `hex` (boolean, default: false): Stream as hexadecimal strings
+
+**Examples:**
+```bash
+# Stream unlimited random bytes
+curl -N "http://localhost:8787/stream"
+
+# Stream exactly 1MB
+curl -N "http://localhost:8787/stream?bytes=1048576"
+
+# Stream as hex
+curl -N "http://localhost:8787/stream?hex=true"
+```
+
+### 4. List Cameras (`/cameras`)
+
+List available camera devices on the system.
+
+**Example:**
+```bash
+curl "http://localhost:8787/cameras"
+```
+
+**Response:**
+```json
+{
+  "cameras": [
+    {
+      "index": 0,
+      "human_name": "FaceTime HD Camera",
+      "description": "Built-in camera",
+      "misc": ""
+    }
+  ]
+}
+```
+
+### 5. Health Check (`/health`)
+
+Check if the TRNG server is running.
+
+**Example:**
+```bash
+curl "http://localhost:8787/health"
+```
+
+**Response:** `ok`
+
+## MCP Integration
+
+The API implements the Model Context Protocol (MCP) specification, allowing AI assistants and other MCP clients to discover and use the TRNG service automatically.
+
+### MCP Tools
+
+The following tools are exposed via MCP:
+
+1. **get-random**: Generate random bytes (cryptographically secure)
+2. **get-raw**: Extract raw sensor data
+3. **get-stream**: Stream random bytes continuously
+4. **list-cameras**: Discover available cameras
+5. **health-check**: Verify server status
+
+### Self-Referencing URLs
+
+The MCP endpoint (`/.well-known/mcp.json`) automatically detects the request's hostname from:
+- HTTP `Host` header
+- `X-Forwarded-Proto` header (for reverse proxy scenarios)
+
+This ensures URLs in the MCP response always reference the correct origin, whether accessed via:
+- `localhost:8787`
+- `trng.example.com`
+- Behind a reverse proxy with forwarded headers
+
+## Usage Examples
+
+### Python
+```python
+import requests
+
+# Get 32 random bytes
+response = requests.get("http://localhost:8787/random?bytes=32")
+random_bytes = response.content
+
+# Get hex string
+response = requests.get("http://localhost:8787/random?bytes=64&hex=true")
+hex_string = response.text
+```
+
+### JavaScript/Node.js
+```javascript
+// Get random bytes
+const response = await fetch("http://localhost:8787/random?bytes=32");
+const buffer = await response.arrayBuffer();
+const bytes = new Uint8Array(buffer);
+
+// Stream random data
+const stream = await fetch("http://localhost:8787/stream?bytes=1024");
+const reader = stream.body.getReader();
+// ... read chunks
+```
+
+### curl
+```bash
+# Basic usage
+curl "http://localhost:8787/random?bytes=32&hex=true"
+
+# Save to file
+curl "http://localhost:8787/random?bytes=1024" -o random.bin
+
+# Stream
+curl -N "http://localhost:8787/stream"
+```
+
+## Limitations
+
+- Maximum 1MB per request (`/random` and `/raw`)
+- Maximum 4 concurrent requests
+- Requires a camera device with covered lens
+- Performance depends on camera frame rate
+
+## Security Notes
+
+- No authentication required (intended for local/trusted networks)
+- Random data is cryptographically secure when using `/random` endpoint
+- Raw endpoint (`/raw`) provides unprocessed sensor data
+- Consider rate limiting in production deployments
+
+## See Also
+
+- `TECHNICAL.md` - Technical implementation details
+- `README.md` - Project overview and setup instructions

src/main.rs

@@ -5,7 +5,7 @@
 use axum::{
     body::Body,
     extract::Query,
-    http::{header, StatusCode},
+    http::{header, HeaderMap, StatusCode, Uri},
     response::{Html, IntoResponse, Response, Json},
     routing::get,
     Router,
@@ -77,7 +77,10 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
         .route("/raw", get(get_raw))
         .route("/stream", get(get_stream))
         .route("/health", get(health))
-        .route("/.well-known/mcp.json", get(mcp_wellknown));
+        .route("/.well-known/mcp.json", get(mcp_wellknown))
+        .route("/docs", get(get_docs))
+        .route("/docs/skill.md", get(get_skill_md))
+        .route("/docs/mcp.json", get(mcp_wellknown));
 
     let addr = format!("0.0.0.0:{}", port);
     println!("Camera QRNG (LavaRnd-style) on http://{}", addr);
@@ -89,6 +92,156 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
 async fn index() -> Html<&'static str> { Html(INDEX_HTML) }
 async fn health() -> &'static str { "ok" }
 
+async fn get_docs() -> Html<String> {
+    // Convert markdown to HTML (simple version)
+    let html = format!(
+        r#"<!DOCTYPE html>
+<html>
+<head>
+    <meta charset="utf-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1">
+    <title>Camera TRNG API Documentation</title>
+    <style>
+        body {{ font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif; max-width: 900px; margin: 0 auto; padding: 20px; line-height: 1.6; }}
+        h1 {{ border-bottom: 2px solid #333; padding-bottom: 10px; }}
+        h2 {{ margin-top: 30px; border-bottom: 1px solid #ccc; padding-bottom: 5px; }}
+        code {{ background: #f4f4f4; padding: 2px 6px; border-radius: 3px; font-family: "Monaco", "Courier New", monospace; }}
+        pre {{ background: #f4f4f4; padding: 15px; border-radius: 5px; overflow-x: auto; }}
+        pre code {{ background: none; padding: 0; }}
+        a {{ color: #0066cc; text-decoration: none; }}
+        a:hover {{ text-decoration: underline; }}
+        .endpoint {{ background: #e8f4f8; padding: 15px; margin: 15px 0; border-left: 4px solid #0066cc; border-radius: 3px; }}
+    </style>
+</head>
+<body>
+    <h1>Camera TRNG API Documentation</h1>
+    <p><a href="/docs/skill.md">View as Markdown</a> | <a href="/docs/mcp.json">View MCP JSON</a> | <a href="/">Back to Home</a></p>
+    <hr>
+    {}
+</body>
+</html>"#,
+        markdown_to_html(SKILL_MD)
+    );
+    Html(html)
+}
+
+async fn get_skill_md() -> Response {
+    Response::builder()
+        .header(header::CONTENT_TYPE, "text/markdown; charset=utf-8")
+        .body(Body::from(SKILL_MD))
+        .unwrap()
+}
+
+fn markdown_to_html(md: &str) -> String {
+    use std::fmt::Write;
+    let mut html = String::new();
+    let mut in_code_block = false;
+    let mut code_content = String::new();
+    
+    for line in md.lines() {
+        if line.starts_with("```") {
+            if in_code_block {
+                write!(html, "<pre><code>{}</code></pre>
+", escape_html(&code_content)).unwrap();
+                code_content.clear();
+                in_code_block = false;
+            } else {
+                in_code_block = true;
+            }
+            continue;
+        }
+        
+        if in_code_block {
+            code_content.push_str(line);
+            code_content.push_str("\n");
+            continue;
+        }
+        
+        let trimmed = line.trim();
+        if trimmed.is_empty() {
+            html.push_str("<br>\n");
+        } else if trimmed.starts_with("### ") {
+            write!(html, "<h3>{}</h3>
+", escape_html(&trimmed[4..])).unwrap();
+        } else if trimmed.starts_with("## ") {
+            write!(html, "<h2>{}</h2>
+", escape_html(&trimmed[3..])).unwrap();
+        } else if trimmed.starts_with("# ") {
+            write!(html, "<h1>{}</h1>
+", escape_html(&trimmed[2..])).unwrap();
+        } else {
+            // Simple inline processing
+            let mut processed = String::new();
+            let mut chars = trimmed.chars().peekable();
+            while let Some(ch) = chars.next() {
+                match ch {
+                    '`' => {
+                        let mut code = String::new();
+                        while let Some(&next) = chars.peek() {
+                            if next == '`' {
+                                chars.next();
+                                write!(processed, "<code>{}</code>", escape_html(&code)).unwrap();
+                                break;
+                            }
+                            code.push(chars.next().unwrap());
+                        }
+                    }
+                    '*' if chars.peek() == Some(&'*') => {
+                        chars.next();
+                        let mut bold = String::new();
+                        while let Some(&next) = chars.peek() {
+                            if next == '*' && chars.clone().nth(1) == Some('*') {
+                                chars.next();
+                                chars.next();
+                                write!(processed, "<strong>{}</strong>", escape_html(&bold)).unwrap();
+                                break;
+                            }
+                            bold.push(chars.next().unwrap());
+                        }
+                    }
+                    '[' => {
+                        let mut text = String::new();
+                        let mut url = String::new();
+                        while let Some(&next) = chars.peek() {
+                            if next == ']' {
+                                chars.next();
+                                if chars.peek() == Some(&'(') {
+                                    chars.next();
+                                    while let Some(&next) = chars.peek() {
+                                        if next == ')' {
+                                            chars.next();
+                                            write!(processed, "<a href=\"{}\">{}</a>", url, escape_html(&text)).unwrap();
+                                            break;
+                                        }
+                                        url.push(chars.next().unwrap());
+                                    }
+                                }
+                                break;
+                            }
+                            text.push(chars.next().unwrap());
+                        }
+                    }
+                    _ => processed.push(ch),
+                }
+            }
+            write!(html, "<p>{}</p>
+", processed).unwrap();
+        }
+    }
+    
+    html
+}
+
+fn escape_html(s: &str) -> String {
+    s.replace("&", "&amp;")
+        .replace("<", "&lt;")
+        .replace(">", "&gt;")
+        .replace("\"", "&quot;")
+}
+
+
+
+
 async fn get_cameras() -> Response {
     match tokio::task::spawn_blocking(list_cameras).await {
         Ok(Ok(cameras)) => Json(serde_json::json!({ "cameras": cameras })).into_response(),
@@ -97,27 +250,98 @@ async fn get_cameras() -> Response {
     }
 }
 
-async fn mcp_wellknown() -> Json<serde_json::Value> {
+async fn mcp_wellknown(headers: HeaderMap, _uri: Uri) -> Json<serde_json::Value> {
+    // Extract origin from request headers (Host header + scheme)
+    let host = headers
+        .get("host")
+        .and_then(|h| h.to_str().ok())
+        .unwrap_or("localhost:8787");
+    
+    // Determine scheme from X-Forwarded-Proto or default to http
+    let scheme = headers
+        .get("x-forwarded-proto")
+        .and_then(|h| h.to_str().ok())
+        .unwrap_or("http");
+    
+    let origin = format!("{}://{}", scheme, host);
+    
+    // Build URL templates as strings first
+    let random_url = format!("{}/random?bytes={{bytes}}&hex={{hex}}", origin);
+    let raw_url = format!("{}/raw?bytes={{bytes}}", origin);
+    let stream_url = format!("{}/stream?bytes={{bytes}}&hex={{hex}}", origin);
+    let cameras_url = format!("{}/cameras", origin);
+    let health_url = format!("{}/health", origin);
+    let mcp_url = format!("{}/.well-known/mcp.json", origin);
+    
     Json(json!({
         "mcp": {
             "spec_version": "2026-01-21",
             "status": "active",
             "servers": [],
-            "tools": [{
+            "tools": [
-                "name": "camera-qrng",
+                {
-                "description": "High-throughput quantum RNG using thermal noise from covered camera sensor",
+                    "name": "get-random",
-                "url_template": "{origin}/random?bytes={bytes}&hex={hex}",
+                    "description": "Get cryptographically secure random bytes from camera sensor entropy",
-                "capabilities": ["random-generation", "entropy-source", "quantum"],
+                    "url_template": random_url,
-                "auth": { "type": "none" },
+                    "capabilities": ["random-generation", "entropy-source", "quantum"],
-                "parameters": {
+                    "auth": { "type": "none" },
-                    "bytes": { "type": "integer", "default": 32, "max": 1048576 },
+                    "parameters": {
-                    "hex": { "type": "boolean", "default": false }
+                        "bytes": { "type": "integer", "default": 32, "min": 1, "max": 1048576, "description": "Number of random bytes to generate (max 1MB)" },
+                        "hex": { "type": "boolean", "default": false, "description": "Return bytes as hexadecimal string instead of binary" }
+                    }
+                },
+                {
+                    "name": "get-raw",
+                    "description": "Get raw LSB (least significant bit) data from camera sensor without cryptographic extraction",
+                    "url_template": raw_url,
+                    "capabilities": ["entropy-source", "raw-data"],
+                    "auth": { "type": "none" },
+                    "parameters": {
+                        "bytes": { "type": "integer", "default": 65536, "min": 1, "max": 1048576, "description": "Number of raw bytes to extract (max 1MB)" }
+                    }
+                },
+                {
+                    "name": "get-stream",
+                    "description": "Stream continuous random bytes (SSE format). Use ?bytes=N to limit total bytes, ?hex=true for hex output",
+                    "url_template": stream_url,
+                    "capabilities": ["random-generation", "entropy-source", "quantum", "streaming"],
+                    "auth": { "type": "none" },
+                    "parameters": {
+                        "bytes": { "type": "integer", "optional": true, "description": "Total bytes to stream (omit for unlimited)" },
+                        "hex": { "type": "boolean", "default": false, "description": "Stream as hexadecimal strings" }
+                    }
+                },
+                {
+                    "name": "list-cameras",
+                    "description": "List available camera devices",
+                    "url_template": cameras_url,
+                    "capabilities": ["device-discovery"],
+                    "auth": { "type": "none" },
+                    "parameters": {}
+                },
+                {
+                    "name": "health-check",
+                    "description": "Check if the TRNG server is running",
+                    "url_template": health_url,
+                    "capabilities": ["health"],
+                    "auth": { "type": "none" },
+                    "parameters": {}
                 }
-            }]
+            ],
+            "resources": [
+                {
+                    "uri": mcp_url,
+                    "name": "MCP Documentation",
+                    "description": "This MCP endpoint documentation",
+                    "mimeType": "application/json"
+                }
+            ]
         }
     }))
 }
 
+
+
 async fn get_random(Query(params): Query<RandomQuery>) -> Response {
     let current = ACTIVE_REQUESTS.fetch_add(1, Ordering::SeqCst);
     if current >= MAX_CONCURRENT {
@@ -222,3 +446,4 @@ async fn get_stream(Query(params): Query<StreamQuery>) -> Response {
 
 
 const INDEX_HTML: &str = include_str!("index.html");
+const SKILL_MD: &str = include_str!("../skill.md");