Perl SDK

Enables building MCP (Model Context Protocol) servers in Perl by providing async event-loop integration through Mojolicious's non-blocking I/O framework. Handles JSON-RPC 2.0 message serialization, bidirectional communication over stdio/WebSocket transports, and automatic request routing to handler methods. Uses Mojolicious's Mojo::IOLoop for event-driven request processing without blocking.

Implements MCP client-side protocol handling including JSON-RPC 2.0 message construction, request ID tracking, response correlation, and error handling. Validates incoming messages against MCP schema, manages request timeouts, and provides typed method calls for standard MCP operations (list_resources, call_tool, read_resource). Uses Perl's type system and validation libraries to ensure protocol compliance.

Provides declarative syntax for defining MCP resources (files, APIs, databases) and tools (callable functions) with JSON Schema validation. Developers define resource metadata (name, description, MIME type, URI template) and tool signatures (parameters, return types) using Perl data structures or builder methods. The SDK automatically generates JSON Schema from Perl type hints and validates incoming requests against these schemas before invoking handlers.

Abstracts MCP communication over multiple transport protocols through a pluggable transport interface. Supports stdio (for local tool integration), WebSocket (for persistent connections), and HTTP (for request-response patterns). Each transport handles framing, serialization, and connection lifecycle independently. The SDK routes messages through the appropriate transport based on server/client configuration without requiring application code changes.

Enables non-blocking request handling using Perl's Future or Promise libraries integrated with Mojolicious's Mojo::IOLoop event reactor. Tool handlers can return futures that resolve asynchronously, allowing the server to process multiple concurrent requests without blocking. The SDK automatically manages future resolution, error propagation, and timeout handling within the event loop.

Provides Mojolicious-style middleware hooks for intercepting and modifying MCP requests and responses before/after handler execution. Developers register middleware that runs in a chain, enabling cross-cutting concerns like logging, authentication, rate limiting, and request transformation. Middleware can short-circuit request processing (e.g., deny unauthorized requests) or modify request/response payloads.

Provides structured error handling that maps Perl exceptions to MCP-compliant error responses with standard error codes (INVALID_REQUEST, METHOD_NOT_FOUND, INVALID_PARAMS, INTERNAL_ERROR, SERVER_ERROR). Developers throw Perl exceptions in tool handlers, and the SDK automatically converts them to JSON-RPC error objects with appropriate codes and messages. Supports custom error codes and error context propagation.

Automatically validates and coerces tool arguments based on JSON Schema definitions before passing to handlers. Converts JSON types to Perl types (strings to numbers, arrays to Perl arrays, objects to hashes), validates constraints (min/max, pattern, enum), and rejects invalid arguments with detailed error messages. Uses JSON Schema validators integrated with Perl type systems.