fastmcp/docs/python-sdk/fastmcp-cli-client.mdx

---
title: client
sidebarTitle: client
---

# `fastmcp.cli.client`


Client-side CLI commands for querying and invoking MCP servers.

## Functions

### `resolve_server_spec` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/cli/client.py#L43" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
resolve_server_spec(server_spec: str | None) -> str | dict[str, Any] | ClientTransport
```


Turn CLI inputs into something ``Client()`` accepts.

Exactly one of ``server_spec`` or ``command`` should be provided.

Resolution order for ``server_spec``:
1. URLs (``http://``, ``https://``) — passed through as-is.
   If ``--transport`` is ``sse``, the URL is rewritten to end with ``/sse``
   so ``infer_transport`` picks the right transport.
2. Existing file paths, or strings ending in ``.py``/``.js``/``.json``.
3. Anything else — name-based resolution via ``resolve_name``.

When ``command`` is provided, the string is shell-split into a
``StdioTransport(command, args)``.


### `coerce_value` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/cli/client.py#L264" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
coerce_value(raw: str, schema: dict[str, Any]) -> Any
```


Coerce a string CLI value according to a JSON-Schema type hint.


### `parse_tool_arguments` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/cli/client.py#L298" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
parse_tool_arguments(raw_args: tuple[str, ...], input_json: str | None, input_schema: dict[str, Any]) -> dict[str, Any]
```


Build a tool-call argument dict from CLI inputs.

A single JSON object argument is treated as the full argument dict.
``--input-json`` provides the base dict; ``key=value`` pairs override.
Values are coerced using the tool's ``inputSchema``.


### `format_tool_signature` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/cli/client.py#L370" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
format_tool_signature(tool: mcp.types.Tool) -> str
```


Build ``name(param: type, ...) -> return_type`` from a tool's JSON schemas.


### `list_command` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/cli/client.py#L641" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
list_command(server_spec: Annotated[str | None, cyclopts.Parameter(help='Server URL, Python file, MCPConfig JSON, or .js file')] = None) -> None
```


List tools available on an MCP server.

**Examples:**

fastmcp list http://localhost:8000/mcp
fastmcp list server.py
fastmcp list mcp.json --json
fastmcp list --command 'npx -y @mcp/server' --resources
fastmcp list http://server/mcp --transport sse


### `call_command` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/cli/client.py#L796" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
call_command(server_spec: Annotated[str | None, cyclopts.Parameter(help='Server URL, Python file, MCPConfig JSON, or .js file')] = None, target: Annotated[str, cyclopts.Parameter(help='Tool name, resource URI, or prompt name (with --prompt)')] = '', *arguments: str) -> None
```


Call a tool, read a resource, or get a prompt on an MCP server.

By default the target is treated as a tool name. If the target
contains ``://`` it is treated as a resource URI. Pass ``--prompt``
to treat it as a prompt name.

Arguments are passed as key=value pairs. Use --input-json for complex
or nested arguments.

**Examples:**

```
fastmcp call server.py greet name=World
fastmcp call server.py resource://docs/readme
fastmcp call server.py analyze --prompt data='[1,2,3]'
fastmcp call http://server/mcp create --input-json '{"tags": ["a","b"]}'
```


### `discover_command` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/cli/client.py#L897" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>

```python
discover_command() -> None
```


Discover MCP servers configured in editor and project configs.

Scans Claude Desktop, Claude Code, Cursor, Gemini CLI, Goose, and
project-level mcp.json files for MCP server definitions.

Discovered server names can be used directly with ``fastmcp list``
and ``fastmcp call`` instead of specifying a URL or file path.

**Examples:**

fastmcp discover
fastmcp discover --source claude-code
fastmcp discover --source cursor --source gemini --json
fastmcp list weather
fastmcp call cursor:weather get_forecast city=London