{"passport":{"unfragile":{"@version":"1.0","version":"2026-05","artifact":{"id":"npm_npm-mcp-proxy","slug":"npm-mcp-proxy","name":"mcp-proxy","type":"mcp","url":"https://www.npmjs.com/package/mcp-proxy","page_url":"https://unfragile.ai/npm-mcp-proxy","categories":["mcp-servers"],"tags":["MCP","SSE","proxy"],"pricing":{"model":"open_source","free":true,"starting_price":null},"status":"active","verified":false},"capabilities":[{"id":"npm_npm-mcp-proxy__cap_0","uri":"capability://tool.use.integration.stdio.to.sse.transport.bridging.for.mcp.servers","name":"stdio-to-sse transport bridging for mcp servers","description":"Converts MCP servers using stdio (standard input/output) transport into HTTP-based Server-Sent Events (SSE) endpoints. The proxy spawns a child process running the stdio-based MCP server, captures its stdout/stderr streams, parses the JSONRPC message protocol, and re-exposes it as an SSE HTTP server. This enables stdio-native MCP servers (which expect bidirectional pipe communication) to be accessed over HTTP without modifying the original server implementation.","intents":["I want to run a stdio-based MCP server in an environment that only supports HTTP/SSE communication","I need to expose a local stdio MCP server to remote clients over the network","I want to integrate a stdio MCP server into a web application without rewriting it for HTTP"],"best_for":["teams integrating stdio-native MCP servers into web or cloud environments","developers building MCP client applications that need HTTP-based server access","infrastructure teams deploying MCP servers in containerized or serverless contexts"],"limitations":["Adds network latency overhead compared to direct stdio communication — each message round-trip crosses HTTP/SSE boundary","Single proxy instance becomes a bottleneck for concurrent clients; no built-in load balancing or connection pooling","Requires the underlying stdio server process to remain stable; crashes require manual restart or external process supervision","SSE is unidirectional server-to-client by design; bidirectional communication requires polling or WebSocket upgrade (not standard SSE)"],"requires":["Node.js 16+ (for native SSE and child_process support)","A working MCP server binary or script that accepts stdio transport","HTTP client capable of consuming SSE streams (browser Fetch API, curl, or MCP client library with SSE support)"],"input_types":["JSONRPC 2.0 messages (as JSON strings)","MCP protocol requests (initialize, call_tool, list_resources, etc.)"],"output_types":["Server-Sent Events (text/event-stream MIME type)","JSONRPC 2.0 response messages","MCP protocol responses (tool results, resource contents, etc.)"],"categories":["tool-use-integration","protocol-bridging"],"confidence":0.5,"matches":0,"success_rate":0},{"id":"npm_npm-mcp-proxy__cap_1","uri":"capability://automation.workflow.child.process.lifecycle.management.for.mcp.servers","name":"child process lifecycle management for mcp servers","description":"Manages the spawning, monitoring, and cleanup of stdio-based MCP server child processes. The proxy handles process creation with proper environment setup, monitors process health and exit codes, captures and logs stderr output, and implements graceful shutdown with signal handling. This ensures the underlying MCP server process remains stable and recovers from transient failures or is properly terminated when the proxy shuts down.","intents":["I want the MCP server process to start automatically when the proxy starts and stop cleanly on shutdown","I need to monitor whether the MCP server process is still running and detect crashes","I want to see error logs from the MCP server to debug integration issues"],"best_for":["operators deploying MCP servers in production environments requiring process supervision","developers debugging MCP server behavior through proxy logs","teams running MCP servers in containers or systemd units where process lifecycle matters"],"limitations":["No automatic restart on crash — requires external process manager (systemd, Docker, PM2) for high availability","Stderr capture is buffered in memory; large error outputs can consume heap without rotation or truncation","Signal propagation depends on Node.js process group handling; zombie processes possible if child ignores SIGTERM","No built-in resource limits (CPU, memory) on child process — runaway servers can exhaust host resources"],"requires":["Node.js 16+ (for child_process.spawn with stdio inheritance)","Executable MCP server binary or script accessible in PATH or via absolute path","Unix-like OS for signal handling (SIGTERM, SIGKILL); Windows behavior differs"],"input_types":["Process configuration (server path, arguments, environment variables)"],"output_types":["Process state (running, exited, crashed)","Stderr logs from child process","Exit codes and signal information"],"categories":["automation-workflow","process-management"],"confidence":0.5,"matches":0,"success_rate":0},{"id":"npm_npm-mcp-proxy__cap_2","uri":"capability://data.processing.analysis.jsonrpc.2.0.message.parsing.and.framing.from.stdio.streams","name":"jsonrpc 2.0 message parsing and framing from stdio streams","description":"Parses JSONRPC 2.0 messages from the raw byte stream of a child process's stdout, handling message boundaries, incomplete frames, and protocol errors. The proxy buffers incoming data, detects complete JSON objects (via brace matching or length prefixes if used by the server), validates JSONRPC structure (id, method, params, result, error fields), and queues messages for processing. This enables reliable bidirectional communication with stdio servers that send multiple messages in rapid succession or split messages across multiple write() calls.","intents":["I need to reliably extract complete JSONRPC messages from a continuous byte stream without losing or duplicating messages","I want to handle cases where the MCP server sends multiple messages in one write() or splits a message across writes","I need to detect and report protocol violations (malformed JSON, missing required JSONRPC fields)"],"best_for":["proxy developers implementing stdio-to-HTTP bridges for JSONRPC-based protocols","teams debugging MCP server communication issues by inspecting raw message flow","builders creating MCP client libraries that need robust frame parsing"],"limitations":["Assumes newline-delimited JSON (NDJSON) or raw JSON objects; does not support length-prefixed framing (used by some MCP implementations)","No timeout on incomplete frames — if server sends partial JSON and hangs, parser blocks indefinitely","Memory usage grows linearly with message size; no streaming parser for large payloads (e.g., multi-MB resource contents)","Error recovery is minimal — a single malformed message can desynchronize the stream if not handled carefully"],"requires":["Node.js 16+ (for Buffer and stream APIs)","MCP server that outputs valid JSONRPC 2.0 messages to stdout","Understanding of JSONRPC 2.0 spec (RFC 7807 or equivalent)"],"input_types":["Raw byte stream (stdout from child process)","UTF-8 encoded JSONRPC 2.0 messages"],"output_types":["Parsed JSONRPC message objects (JavaScript objects with id, method, params, result, error)","Protocol error reports (invalid JSON, missing fields)"],"categories":["data-processing-analysis","protocol-parsing"],"confidence":0.5,"matches":0,"success_rate":0},{"id":"npm_npm-mcp-proxy__cap_3","uri":"capability://tool.use.integration.http.sse.endpoint.exposure.for.mcp.protocol","name":"http/sse endpoint exposure for mcp protocol","description":"Exposes the bridged MCP server as an HTTP endpoint that clients can connect to via Server-Sent Events (SSE). The proxy creates an HTTP server (using Node.js http or Express), implements an SSE endpoint (typically /sse or /stream) that accepts client connections, and streams JSONRPC responses back to connected clients as SSE events. Clients send requests via HTTP POST to a separate endpoint (e.g., /request) or embed them in the SSE connection, and the proxy routes responses back via the SSE stream. This enables web browsers and HTTP-only clients to interact with stdio MCP servers.","intents":["I want to access an MCP server from a web browser or HTTP-only environment","I need to expose an MCP server to multiple concurrent HTTP clients over a network","I want to build a web UI that calls MCP tools without implementing a custom protocol"],"best_for":["web application developers integrating MCP tools into browser-based UIs","teams building HTTP-only MCP clients (e.g., REST API wrappers around MCP)","infrastructure teams exposing local MCP servers to remote networks via HTTP"],"limitations":["SSE is unidirectional (server-to-client only); client-to-server communication requires a separate HTTP POST endpoint or polling, adding latency","No built-in authentication or authorization; requires external middleware (OAuth, API keys) to secure the endpoint","SSE connections are stateless from HTTP perspective; reconnections lose message history unless client implements retry logic","Browser CORS restrictions apply; cross-origin MCP requests require CORS headers or a proxy layer","No compression by default; large MCP responses (e.g., file contents) consume significant bandwidth"],"requires":["Node.js 16+ (for http module or Express.js)","HTTP client library capable of consuming SSE (browser Fetch API, curl, or MCP client SDK)","Network access to the proxy's HTTP port (default often 3000 or 8080)"],"input_types":["HTTP POST requests with JSONRPC message bodies","SSE connection establishment (HTTP GET with Accept: text/event-stream)"],"output_types":["Server-Sent Events (text/event-stream MIME type)","JSONRPC 2.0 responses formatted as SSE event data"],"categories":["tool-use-integration","automation-workflow"],"confidence":0.5,"matches":0,"success_rate":0},{"id":"npm_npm-mcp-proxy__cap_4","uri":"capability://tool.use.integration.request.response.correlation.across.http.sse.boundary","name":"request-response correlation across http/sse boundary","description":"Maintains mapping between JSONRPC request IDs sent by HTTP clients and responses streamed back via SSE, ensuring each client receives only its own responses even when multiple clients are connected simultaneously. The proxy tracks pending requests in a map keyed by JSONRPC id, routes incoming responses from the stdio server back to the correct SSE client connection, and cleans up stale entries on client disconnect. This enables multiplexing of multiple concurrent MCP clients over a single stdio server connection.","intents":["I want multiple web clients to call MCP tools simultaneously without their responses getting mixed up","I need to ensure a client only receives responses to its own requests, not other clients' responses","I want to handle client disconnections gracefully without breaking the stdio server connection"],"best_for":["proxy implementations supporting concurrent HTTP clients","multi-tenant MCP deployments where request isolation is critical","teams building collaborative tools where multiple users interact with the same MCP server"],"limitations":["Request ID collisions possible if clients don't coordinate IDs; no built-in UUID generation or namespacing","Memory leaks possible if responses never arrive (e.g., server crash); requires timeout-based cleanup of stale entries","No ordering guarantees; responses may arrive out-of-order relative to requests if the stdio server processes them asynchronously","Orphaned requests accumulate if clients disconnect without waiting for responses; requires periodic garbage collection"],"requires":["Node.js 16+ (for Map and WeakMap data structures)","JSONRPC clients that include unique id fields in requests","Timeout mechanism (setTimeout or similar) for cleanup"],"input_types":["JSONRPC requests with id field","JSONRPC responses with matching id field"],"output_types":["Routed JSONRPC responses to correct SSE client","Cleanup signals for orphaned requests"],"categories":["tool-use-integration","data-processing-analysis"],"confidence":0.5,"matches":0,"success_rate":0},{"id":"npm_npm-mcp-proxy__cap_5","uri":"capability://tool.use.integration.mcp.protocol.initialization.and.capability.negotiation","name":"mcp protocol initialization and capability negotiation","description":"Handles the MCP initialization handshake between the proxy and the underlying stdio server, exchanging protocol version information, client/server capabilities, and implementation details. The proxy sends an initialize request with client capabilities (supported tools, resources, etc.), receives the server's capabilities response, and caches this metadata for subsequent client requests. This ensures the proxy correctly advertises what the MCP server can do and validates that the server supports required protocol features.","intents":["I want to verify that the MCP server supports the protocol version and features I need","I need to discover what tools, resources, and prompts the MCP server exposes","I want to cache server capabilities to avoid re-negotiating on every client request"],"best_for":["proxy developers implementing full MCP protocol support","teams building MCP client applications that need capability discovery","builders creating MCP server implementations that need to validate client compatibility"],"limitations":["Initialization is synchronous; the proxy blocks until the server responds, delaying startup if the server is slow","No support for dynamic capability changes; if the server's capabilities change after initialization, the proxy won't detect it","Cached capabilities are never refreshed; long-running proxies may serve stale capability information","No fallback if initialization fails; the proxy cannot operate in degraded mode with partial capabilities"],"requires":["MCP server that implements the initialize request/response","Node.js 16+ (for async/await and Promise handling)","Understanding of MCP protocol spec (initialization, capabilities, versions)"],"input_types":["MCP initialize request (client capabilities, protocol version)"],"output_types":["MCP initialize response (server capabilities, implementation name/version)","Cached capability metadata for subsequent requests"],"categories":["tool-use-integration","memory-knowledge"],"confidence":0.5,"matches":0,"success_rate":0},{"id":"npm_npm-mcp-proxy__cap_6","uri":"capability://tool.use.integration.tool.invocation.routing.and.result.streaming","name":"tool invocation routing and result streaming","description":"Routes tool invocation requests from HTTP clients through the stdio server and streams results back via SSE. When a client sends a call_tool request, the proxy forwards it to the stdio server via stdin, waits for the tool_result response, and streams the result back to the client via SSE. The proxy handles tool execution errors, timeout scenarios, and large result payloads that may span multiple SSE events. This enables web clients to invoke MCP tools without understanding the underlying stdio protocol.","intents":["I want to call an MCP tool from a web client and get the result back","I need to handle tool execution errors and timeouts gracefully","I want to stream large tool results (e.g., file contents) back to the client without buffering in memory"],"best_for":["web application developers building UIs that call MCP tools","teams integrating MCP tools into HTTP-based workflows","builders creating MCP client libraries that abstract away stdio transport"],"limitations":["No built-in timeout on tool execution; if a tool hangs, the request blocks indefinitely","Large tool results are buffered in memory before streaming; no streaming parser for incremental result consumption","Tool execution errors are opaque; the proxy cannot distinguish between server errors, tool errors, and protocol errors","No support for tool cancellation; once a tool starts executing, it cannot be interrupted"],"requires":["MCP server that implements call_tool request/response","HTTP client capable of consuming SSE streams","Tool definitions (name, arguments) from server capabilities"],"input_types":["HTTP POST request with call_tool JSONRPC message","Tool name and arguments (JSON object)"],"output_types":["Tool result via SSE (text/event-stream)","Tool execution errors (JSONRPC error response)"],"categories":["tool-use-integration","automation-workflow"],"confidence":0.5,"matches":0,"success_rate":0},{"id":"npm_npm-mcp-proxy__cap_7","uri":"capability://tool.use.integration.resource.access.and.content.retrieval.via.http","name":"resource access and content retrieval via http","description":"Exposes MCP resources (files, documents, etc.) as HTTP endpoints that clients can fetch via read_resource requests. The proxy implements a /resource or /read endpoint that accepts resource URIs, forwards read_resource requests to the stdio server, and returns the resource content as HTTP responses. This enables web clients to browse and retrieve MCP resources without understanding the MCP resource protocol or stdio transport.","intents":["I want to fetch a file or document from an MCP resource server via HTTP","I need to list available resources and their metadata","I want to serve MCP resources as downloadable files in a web application"],"best_for":["web application developers building file browsers or document viewers","teams integrating MCP resource servers into HTTP-based workflows","builders creating MCP client libraries that expose resources as HTTP endpoints"],"limitations":["No built-in caching; every resource request hits the stdio server, causing latency","Large resources are buffered in memory before returning; no streaming response for multi-GB files","No access control; all resources are readable by any HTTP client that can reach the proxy","Resource URI encoding and escaping can be error-prone; special characters may cause lookup failures"],"requires":["MCP server that implements read_resource and list_resources requests","HTTP client capable of making GET/POST requests","Resource URIs in a format the MCP server understands"],"input_types":["HTTP GET/POST request with resource URI","read_resource JSONRPC request"],"output_types":["HTTP response with resource content (text, binary, JSON, etc.)","Resource metadata (MIME type, size, modification time)"],"categories":["tool-use-integration","search-retrieval"],"confidence":0.5,"matches":0,"success_rate":0},{"id":"npm_npm-mcp-proxy__cap_8","uri":"capability://tool.use.integration.prompt.template.discovery.and.invocation","name":"prompt template discovery and invocation","description":"Exposes MCP prompt templates as HTTP endpoints that clients can discover and invoke. The proxy implements a /prompts endpoint that lists available prompts (with descriptions and argument schemas), and a /invoke-prompt endpoint that executes prompts with client-provided arguments. When a client invokes a prompt, the proxy forwards the get_prompt request to the stdio server, receives the rendered prompt text, and returns it via HTTP. This enables web clients to use MCP prompts without understanding the MCP prompt protocol.","intents":["I want to discover what prompts are available from an MCP server","I need to invoke a prompt with specific arguments and get the rendered text back","I want to build a web UI that lets users select and run MCP prompts"],"best_for":["web application developers building prompt management UIs","teams integrating MCP prompts into HTTP-based workflows","builders creating MCP client libraries that expose prompts as HTTP endpoints"],"limitations":["Prompt argument validation is delegated to the MCP server; the proxy cannot validate arguments before forwarding","No caching of prompt definitions; every discovery request hits the stdio server","Prompt rendering is synchronous; if a prompt takes time to render, the HTTP request blocks","No support for streaming prompt results; large rendered prompts are buffered in memory"],"requires":["MCP server that implements list_prompts and get_prompt requests","HTTP client capable of making GET/POST requests","Prompt argument schemas in a format the MCP server understands"],"input_types":["HTTP GET request for prompt discovery","HTTP POST request with prompt name and arguments"],"output_types":["JSON array of prompt metadata (name, description, arguments)","Rendered prompt text (string)"],"categories":["tool-use-integration","text-generation-language"],"confidence":0.5,"matches":0,"success_rate":0},{"id":"npm_npm-mcp-proxy__cap_9","uri":"capability://safety.moderation.error.handling.and.protocol.violation.recovery","name":"error handling and protocol violation recovery","description":"Detects and handles protocol violations, malformed messages, and server errors, returning appropriate JSONRPC error responses to clients. The proxy validates JSONRPC message structure, catches JSON parsing errors, detects missing required fields, and propagates server-side errors (JSONRPC error responses) back to clients. When the stdio server sends invalid data or crashes, the proxy attempts to recover or gracefully close client connections. This ensures clients receive meaningful error information instead of silent failures or connection hangs.","intents":["I want to know when an MCP tool fails or returns an error","I need to detect when the MCP server crashes or becomes unresponsive","I want to receive clear error messages when I send invalid requests"],"best_for":["web application developers building robust MCP client UIs","teams debugging MCP server integration issues","builders creating MCP client libraries that need error handling"],"limitations":["Error messages are opaque; the proxy cannot distinguish between different error types (timeout, crash, protocol error)","No automatic retry logic; clients must implement their own retry strategies","Error recovery is limited; if the stdio server enters an invalid state, the proxy cannot recover without restarting","Large error payloads can consume memory; no truncation or summarization of error messages"],"requires":["Node.js 16+ (for try-catch and error handling)","HTTP client capable of handling JSONRPC error responses","Understanding of JSONRPC 2.0 error format"],"input_types":["Malformed JSONRPC messages","Server error responses (JSONRPC error objects)","Protocol violations (missing fields, invalid types)"],"output_types":["JSONRPC error responses (code, message, data)","HTTP error status codes (400, 500, etc.)"],"categories":["safety-moderation","automation-workflow"],"confidence":0.5,"matches":0,"success_rate":0}],"trust":{"score":27,"verified":false,"data_access_risk":"high","permissions":["Node.js 16+ (for native SSE and child_process support)","A working MCP server binary or script that accepts stdio transport","HTTP client capable of consuming SSE streams (browser Fetch API, curl, or MCP client library with SSE support)","Node.js 16+ (for child_process.spawn with stdio inheritance)","Executable MCP server binary or script accessible in PATH or via absolute path","Unix-like OS for signal handling (SIGTERM, SIGKILL); Windows behavior differs","Node.js 16+ (for Buffer and stream APIs)","MCP server that outputs valid JSONRPC 2.0 messages to stdout","Understanding of JSONRPC 2.0 spec (RFC 7807 or equivalent)","Node.js 16+ (for http module or Express.js)"],"failure_modes":["Adds network latency overhead compared to direct stdio communication — each message round-trip crosses HTTP/SSE boundary","Single proxy instance becomes a bottleneck for concurrent clients; no built-in load balancing or connection pooling","Requires the underlying stdio server process to remain stable; crashes require manual restart or external process supervision","SSE is unidirectional server-to-client by design; bidirectional communication requires polling or WebSocket upgrade (not standard SSE)","No automatic restart on crash — requires external process manager (systemd, Docker, PM2) for high availability","Stderr capture is buffered in memory; large error outputs can consume heap without rotation or truncation","Signal propagation depends on Node.js process group handling; zombie processes possible if child ignores SIGTERM","No built-in resource limits (CPU, memory) on child process — runaway servers can exhaust host resources","Assumes newline-delimited JSON (NDJSON) or raw JSON objects; does not support length-prefixed framing (used by some MCP implementations)","No timeout on incomplete frames — if server sends partial JSON and hangs, parser blocks indefinitely","builder identity is not verified yet","no observed match outcomes yet"],"rank_breakdown":{"adoption":0.05,"quality":0.3,"ecosystem":0.38999999999999996,"match_graph":0.25,"freshness":0.52,"weights":{"adoption":0.25,"quality":0.25,"ecosystem":0.15,"match_graph":0.23,"freshness":0.12}},"observed_outcomes":{"matches":0,"success_rate":0,"avg_confidence":0,"top_intents":[],"last_matched_at":null},"maintenance":{"status":"active","updated_at":"2026-05-24T12:16:23.903Z","last_scraped_at":"2026-05-03T14:23:50.639Z","last_commit":null},"community":{"stars":null,"forks":null,"weekly_downloads":null,"model_downloads":null,"model_likes":null}},"distribution":{"claim_url":"https://unfragile.ai/submit?claim=npm-mcp-proxy","compare_url":"https://unfragile.ai/compare?artifact=npm-mcp-proxy"}},"signature":"/mZajPFRlBj8aDnPHdYfDSAjsKEuwFQUHi14AkVuurARxtUQznTkuz3b4Mfk/svJt15dmIFHmOWGidCS7IgsDA==","signedAt":"2026-06-21T02:48:33.663Z","signedBy":"unfragile.ai","version":1},"_links":{"self":"https://unfragile.ai/api/v1/passport/npm-mcp-proxy","artifact":"https://unfragile.ai/npm-mcp-proxy","verify":"https://unfragile.ai/api/v1/verify?slug=npm-mcp-proxy","publicKey":"https://unfragile.ai/api/v1/trust-passport-public-key","spec":"https://unfragile.ai/trust","schema":"https://unfragile.ai/schema.json","docs":"https://unfragile.ai/docs"}}