Concierge - Production Grade MCP Framework

A backend (also called a provider mode) controls how your tools are presented to the LLM. It sits between the agent and your tools, deciding what the LLM sees and how it invokes them.

Why Backends Matter

When an LLM connects to your MCP server, it calls list_tools() to discover what’s available. The backend determines what comes back: The choice of backend directly affects:

Factor	Impact
Token cost	More tools in context = more tokens per request
Accuracy	Fewer choices = LLM picks the right tool more often
Determinism	Structured execution = more predictable outcomes
Composability	Code/Plan modes let the LLM chain tools in a single turn

Available Backends

Plain

All tools exposed directly. Simple, no wrapping. Best for small APIs.

Search

Semantic search over tools. Agent discovers then calls. Best for large APIs.

Plan

Agent submits a JSON execution plan. Sequential steps with data passing. Best for workflows.

Code

Agent writes Python to call tools. Maximum efficiency. Best for complex logic.

Configuring a Backend

from concierge import Concierge, Config, ProviderType

# Default:Plain
app = Concierge("my-server")

# Explicit
app = Concierge(
    "my-server",
    config=Config(provider_type=ProviderType.SEARCH),
)

The default is Plain. Change it by passing ProviderType.SEARCH, ProviderType.PLAN, or ProviderType.CODE.

Comparison

Backend	LLM sees	Context cost	Best for
Plain	All tools directly	High	Under 20 tools
Search	`search_tools` + `call_tool`	Medium	100+ tools
Plan	`execute_plan`	Low	Multi-step workflows
Code	`execute_code`	Minimal	Complex logic, iteration

Backends + Stages

Backends work on top of stages. If you define stages, the backend only operates on the tools visible in the current stage:not all tools:

app = Concierge(
    "my-server",
    config=Config(provider_type=ProviderType.CODE),
)

app.stages = {"browse": ["search"], "checkout": ["pay"]}
app.transitions = {"browse": ["checkout"], "checkout": []}

In the browse stage with Code mode, tools.pay() raises an error:it’s only available after transitioning to checkout.

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SDK

Backends

Platform

Overview

Why Backends Matter

Available Backends

Plain

Search

Plan

Code

Configuring a Backend

Comparison

Backends + Stages

​Why Backends Matter

​Available Backends

Plain

Search

Plan

Code

​Configuring a Backend

​Comparison

​Backends + Stages

Why Backends Matter

Available Backends

Configuring a Backend

Comparison

Backends + Stages