The Plain backend is the default. Every tool you register is exposed directly:the LLM sees all of them and calls them by name.
Setup
from concierge import Concierge
app = Concierge("my-server")
# That's it:Plain is the default
How It Works
The LLM receives the full list of tools with their names, descriptions, and parameter schemas. It picks one, provides arguments, and Concierge routes the call to your function.
What the LLM Sees
For a server with 3 tools, the LLM’s tool list looks like:
[
{
"name": "search_products",
"description": "Search the product catalog by keyword.",
"inputSchema": {
"type": "object",
"properties": {
"query": {"type": "string"},
"max_results": {"type": "integer", "default": 10}
},
"required": ["query"]
}
},
{
"name": "add_to_cart",
"description": "Add a product to the shopping cart.",
"inputSchema": { ... }
},
{
"name": "checkout",
"description": "Complete the purchase.",
"inputSchema": { ... }
}
]
When to Use
Use Plain when you have a small, focused API:under 20 tools:where every tool is potentially relevant at any point.
- Simple servers with few tools
- Tools that are all equally relevant at any time
- Quick prototyping before adding structure
Bad fit:
- 50+ tools (context bloat)
- Workflows with ordering requirements (use stages)
- Cost-sensitive applications (use Code or Plan)
Example
from concierge import Concierge
app = Concierge("weather")
@app.tool()
def get_forecast(city: str, days: int = 3) -> dict:
"""Get weather forecast for a city."""
return {"city": city, "forecast": [{"day": 1, "temp": 72}]}
@app.tool()
def get_alerts(region: str) -> dict:
"""Get active weather alerts for a region."""
return {"alerts": []}
