@ampersend_ai/modelcontextprotocol-sdk

Provides a TypeScript framework for building Model Context Protocol servers that abstract away transport layer complexity. Implements the MCP specification with support for multiple transport mechanisms (stdio, HTTP, WebSocket) through a pluggable transport interface, allowing developers to define server behavior through request handlers without managing protocol serialization or connection lifecycle directly.

Enables developers to declaratively define tools with JSON Schema specifications and register request handlers that execute when tools are invoked by LLM clients. Uses a handler registry pattern where tools are defined with input schemas, descriptions, and associated callback functions that receive parsed arguments and return structured results, with automatic schema validation before handler execution.

Enables servers to define reusable prompt templates with variable substitution that clients can request and execute. Implements a prompt registry where prompts are defined with descriptions, argument schemas, and template content, allowing clients to invoke prompts with specific arguments and receive rendered prompt text, enabling LLM-agnostic prompt management and reuse across multiple clients.

Allows servers to expose resources (documents, files, data) that LLM clients can read and reference through the MCP protocol. Implements a resource registry where resources are identified by URIs, can have metadata (MIME type, size), and are served through a content retrieval handler that returns either text or binary data, enabling LLMs to access application data without direct file system access.

Implements the MCP protocol's bidirectional messaging pattern where both client and server can initiate requests and receive responses, with automatic request-response correlation using message IDs. Handles the full lifecycle of message exchange including request serialization, response waiting, timeout management, and error propagation, abstracting away the complexity of managing in-flight requests and response routing.

Provides a stdio-based transport implementation that communicates with MCP clients through standard input/output streams, handling line-buffered JSON message serialization and deserialization. Automatically manages process lifecycle, signal handling, and stream cleanup, making it trivial to create MCP servers that work with stdio-based clients like Claude Desktop without manual stream management code.

Implements an HTTP-based transport layer that exposes MCP protocol endpoints over HTTP, handling JSON request/response serialization, routing MCP messages to appropriate handlers, and managing CORS headers for cross-origin requests. Supports both POST-based RPC and potentially GET-based resource retrieval, with automatic content-type negotiation and error response formatting.

Implements a WebSocket-based transport that maintains persistent bidirectional connections between MCP client and server, enabling real-time message exchange without HTTP request-response overhead. Handles WebSocket lifecycle events (connection, disconnection, errors), automatic message framing, and connection recovery, providing lower latency than HTTP while maintaining compatibility with web-based clients.

Leverages TypeScript generics to provide compile-time type safety for tool and resource handlers, automatically inferring argument types from JSON Schema definitions and providing IDE autocomplete for handler parameters. Enables developers to define handlers with full type information without manual type annotations, catching type mismatches at compile time rather than runtime.

Provides structured error handling that maps application errors to MCP protocol-compliant error responses with appropriate error codes, messages, and optional error data. Implements error serialization that preserves error context while conforming to JSON-RPC error format, enabling clients to distinguish between protocol errors, tool execution errors, and resource not found errors.

Handles MCP server initialization handshake where the server advertises its capabilities (supported tools, resources, prompts) to the client during connection setup. Implements the initialization protocol that exchanges server info, protocol version, and capability lists, ensuring client-server compatibility and enabling clients to discover available functionality without manual configuration.