@modelcontextprotocol/inspector

Dynamically discovers and introspects MCP server capabilities by querying the server's resource lists, tool definitions, and prompt templates through the Model Context Protocol. Uses the MCP client library to establish connections and parse server-advertised schemas without requiring pre-built knowledge of server implementations, enabling runtime capability detection across heterogeneous MCP servers.

Provides a web-based or CLI interface for sending raw MCP protocol messages to a connected server and inspecting responses in real-time. Captures request/response payloads, timing information, and error details, allowing developers to trace protocol-level interactions and validate server behavior without writing client code. Implements message formatting, validation, and pretty-printing of JSON payloads.

Renders JSON schemas for MCP tool parameters, resource types, and prompt inputs in a human-readable format with type information, constraints, and descriptions. Parses JSON Schema specifications and generates formatted documentation or interactive UI representations that help developers understand what inputs a tool expects and what outputs it produces, including validation rules and optional/required field indicators.

Manages lifecycle and configuration of MCP server connections across multiple transport types (stdio, HTTP, WebSocket) through a unified interface. Handles connection establishment, authentication, error recovery, and graceful shutdown, abstracting transport-specific details so developers can switch between transport mechanisms without changing application code. Implements connection pooling and multiplexing for efficient resource usage.

Validates incoming and outgoing MCP protocol messages against the MCP specification, checking message structure, required fields, type correctness, and protocol version compatibility. Performs schema validation on request/response payloads and detects protocol violations before they cause runtime errors. Provides detailed error messages identifying which fields violate constraints and why.

Filters and routes requests to MCP servers based on their advertised capabilities (available tools, resources, prompts). Enables selection of the appropriate server from a pool based on required capabilities, and prevents sending requests to servers that don't support the requested operation. Implements capability matching logic that handles partial capability matches and capability versioning.

Streams MCP protocol events (requests, responses, errors, resource updates) in real-time, allowing developers to monitor server activity and client interactions as they occur. Implements event subscription patterns where clients can listen for specific event types and receive notifications with full event context. Supports filtering events by type, source, or content patterns.