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6. MCP Server Registry with stdio / SSE / WebSocket Transports

Status: Accepted Date: 2026-04-07 Domain: api-design, distributed-systems

Context​

Agents need access to a curated catalog of external tools (GitHub, filesystems, internal databases) via the Model Context Protocol. MCP servers ship in three transport flavors and arbitrary trust levels; the platform must register, test, and govern them centrally (PRD §6.5, §8.5).

Decision​

Implement an MCP Registry as a first-class subsystem with CRUD APIs and a UI panel. Support all three transports: stdio (local subprocess), SSE (remote HTTP), and WebSocket (remote persistent). Registration is a multi-step flow that fetches and displays the tool manifest before persisting. Secrets (env vars, auth tokens) are encrypted at rest. The platform itself ships a built-in MCP server that exposes every installed Capability Pack as a typed MCP tool, giving agent frameworks zero-code access (see ADR 003).

Consequences​

Positive: new tools are added by operators in <60 s; all MCP traffic is auditable; agent frameworks integrate via a single MCP-server registration. Negative: stdio servers must be supply-chain reviewed manually; the registry becomes a high-value target for misconfiguration.

§6.5 MCP Server Management, §8.5 MCP Registry Panel, §11.3 MCPServer data model, §13 Agent Consumer Ecosystem