core ¶

MCP protocol types and tool-handler APIs.

This package defines the shared types used by both server/ and client/. It has no dependencies on either — only stdlib and encoding/json.

What belongs here ¶

• JSON-RPC types: Request, Response, Error
• MCP domain types: ToolDef, ResourceDef, PromptDef, Content, Claims
• Tool-handler APIs: Sample(), Elicit(), EmitLog(), EmitProgress(), NotifyResourcesChanged()
• UI metadata types: UIMetadata, UICSPConfig, UIVisibility, AppMIMEType, ToolMeta, ResourceContentMeta
• Extension types: Extension, ExtensionProvider, RefValidator, ClientExtensionCap, UIExtensionID
• Context helpers: ClientSupportsExtension(), ClientSupportsUI()
• Interfaces: Transport, TokenSource, AuthValidator
• Protocol constants: ServerInfo, ClientInfo, ClientCapabilities

What does NOT belong here ¶

• Server implementation (Dispatcher, transports, middleware) → server/
• Client implementation (HTTP transports, reconnection) → client/
• Auth implementation (JWT, PRM, OAuth) → ext/auth/
• Anything that imports server/ or client/