fastmcp/examples/code_mode/server.py
Jeremiah Lowin 404b820144
Add ListTools, search limit, and catalog size annotation to CodeMode (#3359)
* Add tests for two-stage pattern, empty full-detail results, empty inputs

* Add ListTools, search limit, catalog size annotation; split tests

Co-authored-by: Claude <noreply@anthropic.com>

* Remove BM25 internal cap so Search.limit is the sole truncation point

* Pass default_limit to BM25 instead of arbitrary high cap

---------

Co-authored-by: Claude <noreply@anthropic.com>
2026-03-02 18:00:21 -05:00

84 lines
1.9 KiB
Python

"""Example: CodeMode transform — search and execute tools via code.
CodeMode replaces the entire tool catalog with two meta-tools: `search`
(keyword-based tool discovery) and `execute` (run Python code that chains
tool calls in a sandbox). This dramatically reduces round-trips and
context window usage when an LLM needs to orchestrate many tools.
Requires pydantic-monty for the sandbox:
pip install "fastmcp[code-mode]"
Run with:
uv run python examples/code_mode/server.py
"""
from fastmcp import FastMCP
from fastmcp.experimental.transforms.code_mode import CodeMode
mcp = FastMCP("CodeMode Demo")
@mcp.tool
def add(a: int, b: int) -> int:
"""Add two numbers together."""
return a + b
@mcp.tool
def multiply(x: float, y: float) -> float:
"""Multiply two numbers."""
return x * y
@mcp.tool
def fibonacci(n: int) -> list[int]:
"""Generate the first n Fibonacci numbers."""
if n <= 0:
return []
seq = [0, 1]
while len(seq) < n:
seq.append(seq[-1] + seq[-2])
return seq[:n]
@mcp.tool
def reverse_string(text: str) -> str:
"""Reverse a string."""
return text[::-1]
@mcp.tool
def word_count(text: str) -> int:
"""Count the number of words in a text."""
return len(text.split())
@mcp.tool
def to_uppercase(text: str) -> str:
"""Convert text to uppercase."""
return text.upper()
@mcp.tool
def list_files(directory: str) -> list[str]:
"""List files in a directory."""
import os
return os.listdir(directory)
@mcp.tool
def read_file(path: str) -> str:
"""Read the contents of a file."""
with open(path) as f:
return f.read()
# CodeMode collapses all 8 tools into just `search` + `execute`.
# The LLM discovers tools via keyword search, then writes Python
# scripts that chain multiple tool calls in a single round-trip.
mcp.add_transform(CodeMode())
if __name__ == "__main__":
mcp.run()