### What “Fast‑MCP” is today – and why your code keeps breaking  

| What you tried to import | Why it fails | What to do instead |
|---|---|---|
| `from fastmcp.servers …` / `fastmcp.client.sse` | **The layout you remember was removed.**<br/>As of *FastMCP ≥ 1.0* the project focuses **only on helping you *write servers***.  All *client‑side* helpers (SSE transport, `FastClientSession`, etc.) were merged into the **official `mcp` Python SDK** and deleted from FastMCP. citeturn14view0 | • Keep using the **`mcp` SDK** for talking to servers (list tools, call tools).<br/>• Use **FastMCP only to *build* servers you want to expose to Claude/Swarms**. |
| `NotRequired` from `typing` on Python ≤ 3.10 | `typing.NotRequired` is available only in 3.11+. | Import it from `typing_extensions`: <br/>```python<br/>from typing_extensions import NotRequired, TypedDict<br/>``` |

---

## 1 · Update your Swarms integration (client side)

```diff
- from fastmcp.client.sse import sse_client
- from fastmcp import FastClientSession as ClientSession
+ from mcp import ClientSession                  # unchanged from old codebase
+ from mcp.client.sse import sse_client          # still lives in `mcp`
```

Nothing else in your `MCPServer*` helper classes has to change – the wire protocol is the same.

### Add the missing `mcp_servers` field to `Agent`

```diff
class Agent:
     def __init__(self, 
                  ...
-                 tools_list_dictionary: Optional[List[Dict[str, Any]]] = None,
+                 tools_list_dictionary: Optional[List[Dict[str, Any]]] = None,
+                 mcp_servers: Optional[list[MCPServerSseParams]] = None,
                  *args, **kwargs):
         ...
         self.mcp_servers = mcp_servers or []
```

and inside `handle_tool_init` gate tool execution with `if self.mcp_servers:` instead of accessing an attribute that did not exist.

---

## 2 · Build (or re‑use) servers with FastMCP

FastMCP is perfect for *authoring* a server – e.g. a tiny calculator you can smoke‑test against Swarms:

```python
# calc_server.py
from fastmcp import FastMCP

mcp = FastMCP("Calc")           # the object name *must* be `mcp`, `app`, or `server`

@mcp.tool()
def add(a: int, b: int) -> int:
    """Add two numbers"""
    return a + b
```

Run it locally:

```bash
pip install fastmcp mcp           # FastMCP 2.2.0 pulls the right deps
fastmcp dev calc_server.py        # opens the GUI inspector
```

or keep it running for Swarms with

```bash
fastmcp run calc_server.py
```

---

## 3 · Connect from Swarms (smoke‑test)

```python
from swarms import Agent
from swarms.tools.mcp_integration import MCPServerSseParams

server_local = MCPServerSseParams(
    url="http://127.0.0.1:6274",          # the URL printed by `fastmcp run`
    headers={"Content-Type": "application/json"},
)

agent = Agent(
    agent_name      = "Math‑Smoke‑Tester",
    system_prompt   = "You call external MCP tools to do the math.",
    mcp_servers     = [server_local],     # <-- now it exists
    max_loops       = 1,
)

print(agent.run("Use the add tool to add 2 and 2"))
```

If the calculator server is reachable, Swarms will:

1. Receive the LLM’s function‑call JSON,
2. Pass it to `batch_mcp_flow`,
3. The MCP client will POST to `http://127.0.0.1:6274`,
4. Tool returns `4`, which your `Agent` prints.

---

## 4 · Where to read the current docs

* **FastMCP PyPI** – installation & quick‑start citeturn14view0  
* **Official MCP SDK** (client utilities) – <https://github.com/modelcontextprotocol/python-sdk>  

Stick to this split and you can forget about missing modules or mismatched versions.