ReddRadar
Agent skill
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.
Install this agent skill to your Project
npx add-skill https://github.com/Jamie-BitFlight/claude_skills/tree/main/plugins/fastmcp-creator/skills/fastmcp-client-cli
SKILL.md
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' |
| 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.
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