mcp-valve-1.0.0 is not a library.

mcp-valve

A unified MCP (Model Context Protocol) client that works with any MCP server through configurable profiles.

Design Philosophy

This tool is a thin wrapper around the MCP protocol.

Tools are called by providing JSON arguments that conform to the inputSchema from tools/list
No validation or field name conversion occurs - the MCP server's schema is the source of truth
If tools/list shows a field named X, use X exactly as-is in your JSON

Installation

cargo install mcp-valve
# Or build from source:
cargo build --release

Quick Start

# List configured servers
mcp-valve list-servers

# List tools from a server
mcp-valve --server playwright list-tools

# Call a tool
mcp-valve --server playwright call browser_navigate --args '{"url":"https://example.com"}'

# Read args from stdin
echo '{"url":"https://example.com"}' | mcp-valve --server playwright call browser_navigate --args -

# Daemon mode (persistent connection)
mcp-valve --server playwright start-daemon --server-args '["--gui"]'
mcp-valve --server playwright call browser_click --args '{"element":"Submit","ref":"e1"}'
mcp-valve --server playwright daemon-status
mcp-valve --server playwright stop-daemon

Configuration

Server profiles are defined in ~/.claude/scripts/mcp-servers.json:

{
  "playwright": {
    "command": ["npx", "@playwright/mcp@latest"],
    "default_args": ["--headless"],
    "supports_daemon": true,
    "description": "Playwright browser automation",
    "env": {}
  },
  "zen": {
    "command": ["/path/to/python"],
    "default_args": ["/path/to/server.py"],
    "supports_daemon": false,
    "description": "Zen MCP multi-AI model integration",
    "env": {}
  }
}

Profile Options

Field	Type	Description
`command`	`string[]`	Command and initial args to start the server
`default_args`	`string[]`	Default arguments (overridden by `--server-args`)
`supports_daemon`	`bool`	Enable daemon mode for persistent connections
`description`	`string`	Human-readable description
`env`	`object`	Environment variables to set

Template Variables

Arguments support template expansion:

Variable	Expands To
`{profile_dir}`	`.mcp-profile/<server-name>`
`{pid}`	Current process ID
`{cwd}`	Current working directory

Commands

Command	Description
`list-servers`	Show all configured servers
`list-tools`	List available tools from server
`call <tool>`	Call a tool with JSON arguments
`shell`	Interactive REPL mode
`start-daemon`	Start persistent daemon
`stop-daemon`	Stop running daemon
`daemon-status`	Check daemon status

Daemon Mode

For servers that support it (supports_daemon: true), daemon mode keeps a persistent MCP connection:

# Start daemon (creates .mcp-profile/<server>/ in current directory)
mcp-valve --server playwright start-daemon

# Calls automatically route through daemon
mcp-valve --server playwright call browser_navigate --args '{"url":"https://example.com"}'

# Check status
mcp-valve --server playwright daemon-status

# Stop daemon
mcp-valve --server playwright stop-daemon

Directory matters: Daemon state is stored in .mcp-profile/ in the current working directory. Different directories = separate daemon instances.

Auto-Fallback

When daemon is running, call automatically uses it. If daemon fails, falls back to STDIO mode.

Technical Details

Protocol: MCP 2025-06-18 (JSON-RPC 2.0)
Transport: STDIO (default) / Unix socket (daemon)
Platform: Unix-like systems (uses nix crate for process management)

Dependencies

clap - CLI parsing
serde / serde_json - JSON serialization
anyhow - Error handling
nix - Unix system calls (umask, setsid, signals)

License

MIT

mcp-valve 1.0.0