MCPCore vs mcp.run: Which One Do You Need?
mcp.run is a registry of sandboxed, Wasm-based tool servlets. MCPCore is a hosting and building platform for MCP servers written in JavaScript. Here is how the two approaches differ.
mcp.run and MCPCore take different technical approaches to the same general goal: giving an AI model tools it can call safely. mcp.run does this through sandboxed WebAssembly modules. MCPCore does it through a hosted server model built around plain JavaScript.
What mcp.run Actually Offers
mcp.run is a registry of tool "servlets" that run sandboxed using the Extism/XTP WebAssembly runtime, multiplexed into a single transport server. It supports "profiles," which are curated sets of tools, and can generate tools automatically from an OpenAPI specification. Tools can run locally in a sandbox or be hosted remotely. This is a distinct architectural approach: the Wasm sandbox is the security boundary, rather than a server-level authentication layer.
What MCPCore Offers Instead
MCPCore hosts a full MCP server per project, written in plain JavaScript in a browser IDE, with security handled at the server level: four authentication modes, encrypted secrets, and per-server rate limiting. Rather than composing pre-built servlets, you write tool logic directly, with AI-assisted code generation and instant live testing before anything goes live.
Side by Side
| mcp.run | MCPCore | |
|---|---|---|
| Security model | Wasm sandbox per servlet | Server-level auth (4 modes) + encrypted secrets |
| Tool authoring | Compose existing servlets, or generate from OpenAPI | Write JavaScript directly in a browser IDE |
| Runtime | Wasm (Extism/XTP) | JavaScript |
| Best for | Composing sandboxed, reusable tool servlets | Building and hosting original server-side tools |
When mcp.run Makes Sense
If the Wasm sandboxing model fits your security requirements, or you want to compose tools from a registry of existing servlets rather than writing server logic from scratch, mcp.run's approach is purpose-built for that.
When MCPCore Makes Sense
If you want to write tool logic directly in JavaScript, with a browser IDE, AI-assisted generation, and server-level authentication and secrets management, MCPCore's model is more familiar to most developers building custom, one-off tools rather than composing from a registry.
Get started free or see MCP server builder for how tool creation works.
Details on mcp.run reflect publicly available information as of mid-2026. Verify current specifics directly with mcp.run's own documentation before making a decision.