v3.0.0b1: This Beta Work
FastMCP 3.0 rebuilds the framework around three primitives: components, providers, and transforms. Providers source components dynamically—from decorators, filesystems, OpenAPI specs, remote servers, or anywhere else. Transforms modify components as they flow to clients—renaming, namespacing, filtering, securing. The features that required specialized subsystems in v2 now compose naturally from these building blocks.
🔌 Provider Architecture unifies how components are sourced. FileSystemProvider discovers decorated functions from directories with optional hot-reload. SkillsProvider exposes agent skill files as MCP resources. OpenAPIProvider and ProxyProvider get cleaner integrations. Providers are composable—share one across servers, or attach many to one server.
🔄 Transforms add middleware for components. Namespace mounted servers, rename verbose tools, filter by version, control visibility—all without touching source code. ResourcesAsTools and PromptsAsTools expose non-tool components to tool-only clients.
📋 Component Versioning lets you register @tool(version="2.0") alongside older versions. Clients see the highest version by default but can request specific versions. serves different API versions from one codebase.