fastmcp/skills/fastmcp-client-cli/SKILL.md

name	description
fastmcp-client-cli	Query and invoke tools on MCP servers using fastmcp list and fastmcp call. Use when you need to discover what tools a server offers, call tools, or integrate MCP servers into workflows.

FastMCP 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'

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

Workflow Pattern

Discover tools first, then call them:

# 1. See what's available
fastmcp list server.py

# 2. Call a tool
fastmcp call server.py tool_name arg=value

If you call a nonexistent tool, FastMCP suggests close matches.