MCP Protocol

Model Context Protocol v2024-11-05 over stdio. JSON-RPC 2.0 transport, 13 native tools implemented in C, zero-copy message parsing.

v2024-11-05MCP Version
stdioTransport
13Tools
JSON-RPC 2.0Protocol

Overview

scorpiox code implements the Model Context Protocol (MCP) as a native C server. The MCP layer runs over stdio using JSON-RPC 2.0 framing — the AI client connects via stdin/stdout and calls tools through structured JSON messages. All 13 tools are compiled into the binary from sx_tools.c with zero runtime dependencies.

# MCP server architecture (from sx_tools.c)

stdin  ──▶  JSON-RPC parser  ──▶  tool dispatcher  ──▶  result  ──▶  stdout

# All tools compiled into single static binary
# Source: scorpiox/libsxutil/sx_tools.c
# Zero runtime dependencies — no Node.js, no Python, no JVM

Transport Layer

The MCP server uses stdio as its transport — the simplest, most reliable pipe. The AI client spawns the scorpiox binary and communicates via stdin/stdout using newline-delimited JSON-RPC 2.0 messages. No HTTP server, no WebSocket, no port binding.

# Transport: stdio (stdin/stdout)
# Framing: newline-delimited JSON-RPC 2.0
# Each message is a single JSON object terminated by \n

# Client sends request →
{"jsonrpc": "2.0", "id": 1, "method": "tools/list", "params": {}}

# Server responds ←
{"jsonrpc": "2.0", "id": 1, "result": {"tools": [...]}}

Initialization Handshake

Before calling tools, the client must complete the MCP initialization handshake. This establishes the protocol version and declares capabilities.

# Step 1: Client sends initialize request
{"jsonrpc": "2.0", "id": 1, "method": "initialize", "params": {
  "protocolVersion": "2024-11-05",
  "capabilities": {},
  "clientInfo": {"name": "claude-ai", "version": "1.0"}
}}

# Step 2: Server responds with capabilities
{"jsonrpc": "2.0", "id": 1, "result": {
  "protocolVersion": "2024-11-05",
  "capabilities": {"tools": {}},
  "serverInfo": {"name": "scorpiox-code", "version": "1.0.0"}
}}

# Step 3: Client sends initialized notification
{"jsonrpc": "2.0", "method": "notifications/initialized", "params": {}}

JSON-RPC Methods

The MCP server handles 4 JSON-RPC methods. All tool invocations go through tools/call.

Method Direction Description
initialize client → server Initialize MCP session with protocol version and client capabilities
notifications/initialized client → server Notification sent after successful initialization handshake
tools/list client → server List all tools available from the MCP server
tools/call client → server Call a specific tool with JSON arguments and receive result
# Example: calling the Bash tool
{"jsonrpc": "2.0", "id": 42, "method": "tools/call", "params": {
  "name": "Bash",
  "arguments": {"command": "ls -la /tmp", "timeout": 5000}
}}

# Server response
{"jsonrpc": "2.0", "id": 42, "result": {
  "content": [{"type": "text", "text": "total 48\ndrwxrwxrwt 12 root root ..."}],
  "isError": false
}}

Tool Catalog (13)

All tools are implemented in scorpiox/libsxutil/sx_tools.c and compiled into the static binary. Each tool declares a JSON Schema for input validation.

Bash shell

Execute a bash command

Parameters: command, timeout
Required: command
ReadImage filesystem

Read an image file and display it visually

Parameters: file_path
Required: file_path
ReadDocs web

Fetch URL content as markdown via headless browser

Parameters: url, format, wait_ms
Required: url
WebSearch search

Search the web using 11 engines concurrently

Parameters: query
Required: query
TaskManager workflow

Manage persistent tasks with create/add/complete

Parameters: action, query, task_id, step_id, text
Required: action, query
PlanMode workflow

Manage plan mode for complex tasks

Parameters: action, goal, plan_file
Required: action
AskUserQuestion interaction

Ask interactive multiple-choice questions via TUI

Parameters: questions_json
Required: questions_json
InvokeSkill workflow

Invoke a skill by name for reusable workflows

Parameters: skill_name, arguments
Required: skill_name
BackgroundBash shell

Execute bash command in background, returns immediately

Parameters: command
Required: command
ReadBgOutput shell

Read new output from a background task

Parameters: task_id
Required: task_id
ListBgTasks shell

List all background tasks with status and runtime

Parameters:
Required:
KillBgTask shell

Kill a running background task by ID

Parameters: task_id
Required: task_id
SetCallback workflow

Manage scheduled callback messages with repeats

Parameters: action, message, delay_seconds, repeat_count, callback_id
Required: action

Tool Schema Reference

Complete input_schema for each tool, as declared in the tools/list response.

Bash shell
ParametersTypeStatusDescription
command string required The bash command to execute
timeout integer optional Timeout in milliseconds (default: 30000)
ReadImage filesystem
ParametersTypeStatusDescription
file_path string required The absolute path to the image file
ReadDocs web
ParametersTypeStatusDescription
url string required The URL to fetch
format string optional Output format: text, html, or markdown
wait_ms integer optional Wait time for page load in ms
WebSearch search
ParametersTypeStatusDescription
query string required The search query
TaskManager workflow
ParametersTypeStatusDescription
action string required Action: create, add, complete, list, pending, switch
query string required The search query
task_id integer optional Task ID
step_id integer optional Step ID
text string optional Task name or step text
PlanMode workflow
ParametersTypeStatusDescription
action string required Action: enter, exit, status, json, reset
goal string optional Goal/description
plan_file string optional Path to markdown plan file
AskUserQuestion interaction
ParametersTypeStatusDescription
questions_json string required JSON string with questions and options
InvokeSkill workflow
ParametersTypeStatusDescription
skill_name string required The skill name to invoke
arguments string optional Arguments to pass to the skill
BackgroundBash shell
ParametersTypeStatusDescription
command string required The bash command to execute
ReadBgOutput shell
ParametersTypeStatusDescription
task_id integer required The task ID returned by BackgroundBash
KillBgTask shell
ParametersTypeStatusDescription
task_id integer required The task ID to kill
SetCallback workflow
ParametersTypeStatusDescription
action string required Action: set, list, cancel
message string optional Callback message
delay_seconds integer optional Seconds to wait (1-3600)
repeat_count integer optional Times to fire before cancel
callback_id integer optional Callback slot ID

Configuration

MCP is enabled by default. The server advertises tools capability during initialization. Configuration is handled via scorpiox-env.txt.

# scorpiox-env.txt — MCP-related settings

TOOLS=true                  # Enable MCP tool serving (default: true)
STREAMING=true              # Stream tool results as they arrive
MODEL=sonnet                # AI model for tool-use conversations

# The MCP server binary path is auto-detected:
# Linux:   ~/.scorpiox/scorpiox-code
# macOS:   ~/.scorpiox/scorpiox-code
# Windows: %USERPROFILE%\.scorpiox\scorpiox-code.exe

# Client config (e.g., Claude Desktop mcp_servers.json):
# {"scorpiox": {"command": "~/.scorpiox/scorpiox-code", "args": []}}