# Fastmcp Client CLI

> Drives the FastMCP client CLI (discover, list, call) to inspect and exercise MCP servers from the shell. Use when the user wants to 'list the tools on this MCP server', 'call this MCP tool from the shell', asks 'what MCP servers are configured', wants to 'smoke-test an MCP server's tools', 'inspect an MCP tool's schema', read a resource, get a prompt, or bridge MCP servers into shell-based workflows.

- Skill: `dinglebear-ai/fastmcp-client-cli` (Agent Skill, multi-file: 4 files)
- Install (CLI): `npx skillmds@latest add dinglebear-ai/fastmcp-client-cli`
- Raw SKILL.md: https://api.skillmd.com/api/skills/dinglebear-ai/fastmcp-client-cli/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: AI & ML
- Author: dinglebear-ai (https://skillmd.com/u/dinglebear-ai)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/dinglebear-ai/fastmcp-client-cli

---


# FastMCP CLI: List and Call

Use `fastmcp discover`, `fastmcp list`, and `fastmcp call` to interact with MCP servers from the command line. These commands are FastMCP 3.x client commands and are useful for development, debugging, scripting, and shell-capable agents that do not have native MCP support.

## 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. With `--json`, resources and prompts are included only when `--resources` or `--prompts` is also passed.

## 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 schema-driven: integers, numbers, booleans, arrays, and objects are coerced from strings based on the target tool's input schema. Booleans accept `true`/`false`, `yes`/`no`, and `1`/`0`. Arrays and objects must be valid JSON.

`fastmcp call` can also read a resource URI or get a prompt:

```bash
# Resource URI targets are detected by ://
fastmcp call server.py resource://docs/readme

# Prompt targets require --prompt
fastmcp call server.py summarize --prompt topic=FastMCP
```

## 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` |

Python file targets are launched through `fastmcp run <file> --no-banner`; code in an `if __name__ == "__main__"` block is not used by `fastmcp run`. JSON targets for `list` and `call` must be MCPConfig-style files with an `mcpServers` key. A `fastmcp.json` server config is not a direct client target; start it first with `fastmcp run`.

Servers configured in editor configs (Claude Desktop, Claude Code, Cursor, Goose) or the current directory's `./mcp.json` can be referenced by name. Bare names are rejected if the same name appears in multiple sources. 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
```

HTTP URLs default to Streamable HTTP. The `--transport sse` override is for older SSE-only servers.

## Auth

HTTP targets automatically use OAuth unless disabled. If the server does not require auth, OAuth setup is a no-op. Disable auth or pass a bearer token with `--auth`:

```bash
fastmcp call http://server/mcp tool --auth none
fastmcp list http://server/mcp --auth "Bearer sk-..."
```

Top-level auth is not applied to MCPConfig JSON targets; those transports are resolved per configured server.

## 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, Goose, and `./mcp.json`. Sources: `claude-desktop`, `claude-code`, `cursor`, `goose`, `project`. Claude Code discovery includes global `~/.claude.json` servers and project-scoped entries matching the current working directory.

## 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.

For shell-agent integration, prefer `fastmcp list --json` to gather tool schemas and `fastmcp call --json` to parse content blocks, `is_error`, and structured content reliably.