@waniwani/sdk
MCP ServerFreeWaniWani SDK - MCP event tracking, widget framework, and tools
Capabilities8 decomposed
mcp server event tracking and instrumentation
Medium confidenceProvides a standardized event emission and tracking system for MCP (Model Context Protocol) servers, allowing developers to instrument their tools and resources with structured event data. The SDK wraps MCP server lifecycle and tool invocation events into a unified event bus that can be consumed by external analytics, monitoring, or logging systems without modifying core server logic.
Provides MCP-native event tracking that integrates directly with the Model Context Protocol lifecycle rather than requiring post-hoc instrumentation, enabling first-class event semantics for Claude tool interactions
Purpose-built for MCP servers unlike generic Node.js event emitters, reducing boilerplate and ensuring events capture MCP-specific context (tool name, resource URI, protocol version)
widget framework for mcp tool ui composition
Medium confidenceOffers a declarative component system for building rich user interfaces for MCP tools, allowing developers to define tool output rendering and input forms as composable widget trees. The framework abstracts away protocol-level rendering details and provides a React-like component model that compiles to MCP-compatible output formats (text, markdown, structured blocks).
Provides a React-inspired component model specifically optimized for MCP tool UIs, with built-in support for Claude's native rendering primitives (blocks, tables, forms) rather than generic web component abstraction
Simpler than building custom markdown templates and more maintainable than imperative string concatenation, while remaining fully compatible with Claude's rendering constraints
structured tool definition and schema validation
Medium confidenceEnables developers to define MCP tools with TypeScript-first schemas that automatically generate JSON Schema, input validation, and type-safe handler functions. The SDK uses a builder pattern to compose tool definitions with input parameters, output types, and execution handlers, then validates all invocations against the declared schema before execution.
Uses TypeScript's type system as the single source of truth for tool schemas, eliminating schema-code drift through compile-time code generation rather than runtime reflection
More type-safe than Zod or Yup-based validation because schemas are generated from TypeScript types rather than defined separately, reducing maintenance burden and enabling IDE autocomplete
event-driven tool execution pipeline with middleware
Medium confidenceImplements a middleware-based execution pipeline for MCP tool invocations, allowing developers to inject cross-cutting concerns (logging, rate limiting, caching, authentication) without modifying tool handler code. The pipeline emits events at each stage (before-invoke, after-invoke, on-error) that can be consumed by middleware or external listeners.
Applies Express-like middleware patterns to MCP tool execution, enabling composable, reusable cross-cutting concerns that work across heterogeneous tool implementations without code modification
More flexible than decorator-based approaches because middleware can be added/removed at runtime and composed dynamically, while remaining simpler than building custom execution orchestration
resource-based tool organization and discovery
Medium confidenceProvides a resource abstraction layer that organizes MCP tools into logical groups (resources) with metadata, versioning, and discovery mechanisms. Tools are registered against resources, enabling clients to discover available tools by resource type, query capabilities, and access control policies without enumerating all tools individually.
Introduces a resource-oriented abstraction on top of MCP's flat tool namespace, enabling hierarchical organization and discovery patterns similar to REST API resource models
More scalable than flat tool lists for large suites because it enables filtering and hierarchical discovery, while remaining simpler than building custom tool registry systems
async context propagation for distributed tracing
Medium confidenceAutomatically propagates execution context (trace IDs, user IDs, request metadata) through async call chains in MCP tool handlers using Node.js AsyncLocalStorage. This enables distributed tracing and correlation of logs/events across multiple async operations without explicit context passing through function parameters.
Leverages Node.js AsyncLocalStorage to provide implicit context propagation without requiring explicit parameter threading, enabling cleaner handler code while maintaining full traceability
Simpler than manual context passing through function parameters and more efficient than storing context in global variables, while remaining compatible with modern async/await patterns
tool result caching with ttl and invalidation
Medium confidenceProvides a pluggable caching layer for MCP tool results with configurable time-to-live (TTL), cache key generation strategies, and invalidation patterns. Caching decisions are made based on tool metadata and invocation parameters, allowing developers to cache expensive operations (API calls, database queries) transparently without modifying tool handlers.
Integrates caching as a first-class concern in the tool execution pipeline with metadata-driven cache policies, rather than requiring developers to implement caching manually in each tool handler
More maintainable than manual caching in tool handlers because cache logic is centralized and can be updated globally, while remaining simpler than building custom caching infrastructure
error handling and retry strategies with exponential backoff
Medium confidenceImplements configurable error handling and retry logic for MCP tool invocations with support for exponential backoff, jitter, and circuit breaker patterns. Developers can define retry policies per tool or globally, with fine-grained control over which errors trigger retries and how many attempts are made before failing.
Provides declarative retry and circuit breaker policies that can be applied to tools without modifying handler code, using a configuration-driven approach similar to HTTP client libraries
More maintainable than implementing retry logic in each tool handler and more flexible than hardcoded retry counts, while remaining simpler than building custom resilience frameworks
Capabilities are decomposed by AI analysis. Each maps to specific user intents and improves with match feedback.
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Best For
- ✓MCP server developers building observable, production-grade tools
- ✓Teams implementing usage analytics for Claude-integrated applications
- ✓Developers creating multi-tenant MCP services requiring per-user event tracking
- ✓MCP tool developers building data-rich applications (dashboards, analytics, CRUD interfaces)
- ✓Teams standardizing UI patterns across a suite of Claude-integrated tools
- ✓Developers unfamiliar with Claude's native rendering capabilities who need abstraction
- ✓TypeScript-first MCP server developers prioritizing type safety and DX
- ✓Teams building MCP tool libraries that need to expose consistent, well-documented APIs
Known Limitations
- ⚠Event tracking is asynchronous and non-blocking — no guarantee of delivery if process crashes before flush
- ⚠No built-in event persistence or buffering — requires external event sink (Kafka, HTTP endpoint, file system)
- ⚠Limited to events emitted during active MCP server session — no historical replay or backfill
- ⚠Widget output is constrained by Claude's native rendering capabilities — no custom CSS or JavaScript execution
- ⚠Interactivity is limited to form submission and tool re-invocation — no real-time bidirectional communication
- ⚠Widget tree compilation adds ~50-100ms overhead per tool invocation for complex component hierarchies
Requirements
Input / Output
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WaniWani SDK - MCP event tracking, widget framework, and tools
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