fastmcp-client-cli

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Translated

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.

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Sourcejlowin/fastmcp
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NPX Install

npx skill4agent add jlowin/fastmcp fastmcp-client-cli

Tags

Translated version includes tags in frontmatter
fastmcp-climcp-servercommand-line-toolsworkflow-integrationtool-discovery

SKILL.md Content

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FastMCP CLI: List and Call

Use 
fastmcp list
and 
fastmcp call
to interact with any MCP server from the command line.

Listing Tools

bash
# 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

bash
# 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:
TargetExample
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
:
bash
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
:
bash
fastmcp call http://server/mcp tool --auth none

Discovering Configured Servers

bash
# 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:
bash
# 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.