About fastmcp-client-cli
fastmcp-client-cli provides command-line discovery, listing, and invocation of MCP servers for developers inspecting or using configured servers. It accepts multiple server target types and scans common editor and project configurations.
Key features
- 01Discover configured MCP servers
- 02List tools and their schemas
- 03Call tools with automatic type coercion
- 04Support HTTP, SSE, stdio, and Python files
- 05OAuth and structured output options
Use cases
- 01Find MCP servers configured in editors
- 02Inspect tools exposed by local or remote servers
- 03Run tools from the command line with arguments
- 04Debug tool input and output schemas
MCP support
It connects to MCP servers from the command line to list and invoke their tools. Targets include URLs, Python files, MCPConfig, stdio commands, and discovered configuration names.
Install
Copy the command and run it in a terminal.
npx skills add https:/After installing, type/fastmcp-client-cliin Claude Code to confirm it loaded.
Details
From the project READMEFastMCP CLI: List and Call
Use fastmcp list and fastmcp call to interact with any MCP server from the command line.
Listing Tools
# Remote server
fastmcp list http://localhost:8000/mcp
# Local Python file (runs via fastmcp run automatically)
fastmcp list server.py
# MCPConfig with multiple servers
fastmcp list mcp.json
# Stdio command (npx, uvx, etc.)
fastmcp list --command 'npx -y @modelcontextprotocol/server-github'
# Include full input/output schemas
fastmcp list server.py --input-schema --output-schema
# Machine-readable JSON
fastmcp list server.py --json
# Include resources and prompts
fastmcp list server.py --resources --prompts
Default output shows tool signatures and descriptions. Use --input-schema or --output-schema to include full JSON schemas, --json for structured output.
Calling Tools
# Key=value arguments (auto-coerced to correct types)
fastmcp call server.py greet name=World
fastmcp call server.py add a=3 b=4
# Single JSON object for complex/nested args
fastmcp call server.py create_item '{"name": "Widget", "tags": ["a", "b"]}'
# --input-json with key=value overrides
fastmcp call server.py search --input-json '{"query": "hello", "limit": 5}' limit=10
# JSON output for scripting
fastmcp call server.py add a=3 b=4 --json
Type coercion is automatic: limit=5 becomes an integer, verbose=true becomes a boolean, based on the tool's input schema.
Server Targets
All commands accept the same server targets:
| Target | Example |
|---|---|
| HTTP/HTTPS URL | http://localhost:8000/mcp |
| Python file | server.py |
| MCPConfig JSON | mcp.json (must have mcpServers key) |
| Stdio command | --command 'npx -y @mcp/server' |
| Discovered name | weather or source:name |
Servers configured in editor configs (Claude Desktop, Claude Code, Cursor, Gemini CLI, Goose) or project-level mcp.json can be referenced by name. Use source:name (e.g. claude-code:my-server, cursor:weather) to target a specific source. Run fastmcp discover to see available names.
For SSE servers, pass --transport sse:
fastmcp list http://localhost:8000/mcp --transport sse
Auth
HTTP targets automatically use OAuth (no-ops if the server doesn't require auth). Disable with --auth none:
fastmcp call http://server/mcp tool --auth none
Discovering Configured Servers
# See all MCP servers in editor/project configs
fastmcp discover
# Filter by source
fastmcp discover --source claude-code
# JSON output
fastmcp discover --json
Scans Claude Desktop, Claude Code, Cursor, Gemini CLI, Goose, and ./mcp.json. Sources: claude-desktop, claude-code, cursor, gemini, goose, project.
Workflow Pattern
Discover tools first, then call them:
# 1. See what servers are configured
fastmcp discover
# 2. See what tools a server has
fastmcp list weather
# 3. Call a tool
fastmcp call weather get_forecast city=London
If you call a nonexistent tool, FastMCP suggests close matches.