Extend a specific integration boundary.

Choose the smallest surface

Need	Start with
Read an existing API or repository	A configured data provider
Call an existing MCP tool	The downstream MCP gateway
Add context to your own application	The published SDK
Change runtime-specific processing	The local extension contract for that runtime version

These paths have different lifecycle, security and stability rules.

Inspect local extensions

The reviewed implementation has removed subprocess-plugin commands. lean-ctx plugin returns a removal notice even though the captured full CLI help still lists it. Do not follow that older entry as a plugin installation procedure. Marketplace/addon commands remain Research, not an available public distribution service.

An extension’s sandbox or capability restrictions apply only to its actual execution path. Do not generalize them to native processes, provider calls or arbitrary host tools.

Treat configuration as code

Review executable commands, environment variables, filesystem access and network destinations. Keep credentials outside shared manifests where supported. Pin the extension version and review updates.

Prefer a public contract for products

If you are shipping an application, use the SDK guide and its declared stable surface. Building against internal Rust modules or a local plugin hook does not inherit the SDK’s compatibility promise.

For reusable third-party MCP connections, see MCP connections.

Sources & versions3 references · Reviewed 18 Sept 2026

• mod.rsrust/src/cli/dispatch/mod.rsReviewed checkout
• addon_cmd.rsrust/src/cli/addon_cmd.rsReviewed checkout
• scaffold.rsrust/src/core/providers/scaffold.rsReviewed checkout

Core checkout

5198ea1867

Installed runtime

3.10.2

SDK release

1.1.0

Separate baselines for source, CLI/configuration and SDK contracts. Review does not certify every platform or integration.

Versions & compatibility