mcs-driver-core 0.3.0

Core driver contract for the Model Context Standard.

mcs-driver-core

Core driver contract for the Model Context Standard (MCS).

This package defines the language-agnostic MCSDriver and MCSToolDriver interfaces, metadata classes (DriverMeta, DriverBinding, DriverResponse), extraction strategies, prompt strategies, and optional mixins (ToolCallSignaling, SupportsNativeTools).

It has zero runtime dependencies and weighs only a few kilobytes.

Installation

pip install mcs-driver-core

Quick start

from mcs.driver.core import MCSDriver, DriverMeta, DriverResponse

class MyDriver(MCSDriver):
    ...

Capability detection

Optional features (health checks, native tool-calling via get_native_tool_context, streaming tool-call signaling, …) are advertised as flags in DriverMeta.capabilities. Each optional contract carries its flag as a CAPABILITY constant. There are two operations — detection ("is the feature there?") and invocation ("give me the object that provides it") — and both avoid isinstance:

from mcs.driver.core import DriverMeta, SupportsNativeTools

# detection: a pure read over the (aggregated) capability flags
if driver.meta.has_capability(SupportsNativeTools):
    ...

# invocation: get the layer that satisfies the contract -- typed, no cast,
# works whether `driver` is a plain driver, an orchestrator, or a decorator
if (dc := DriverMeta.resolve_capability(driver, SupportsNativeTools)):
    ctx = dc.get_native_tool_context(model)

Do not rely on isinstance for feature detection. Drivers are composable: a decorator (auth, permission, hooks, …) wraps another driver, satisfies the same MCSDriver / MCSToolDriver interfaces, and is injected via dependency injection — so from the outside it just looks like a driver, and the client cannot know what the stack contains. isinstance only sees the outermost layer and misses capabilities provided deeper in the stack. Each decorator aggregates the inner driver's capabilities and adds its own, so meta.capabilities reflects the whole stack; isinstance does not.

Links

• Homepage: https://www.modelcontextstandard.io
• Source: https://github.com/modelcontextstandard/python-sdk
• Specification: https://modelcontextstandard.io/Specification

License

Apache-2.0