{"version":"2.1.242","anchor":"plugin-registered-tools-are-served-over-a-local-mcp-server","canonical_anchor":"plugin-registered-tools-are-served-over-a-local-mcp-server","heading":"Plugin-registered tools are served over a local MCP server","tier":"internal","area":"Plugins","scope":null,"heads_up":null,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.242\/e\/plugin-registered-tools-are-served-over-a-local-mcp-server","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.242","markdown":"### Plugin-registered tools are served over a local MCP server\n\nTools a plugin registers reach the model through a local loopback MCP server.\n\n**What**\n\nTools a plugin registers are exposed by starting an HTTP server bound to 127.0.0.1 on a random path, which is then registered as an MCP server scoped to that plugin. This is how plugin tools reach the model.\n\n**Details**\n\n- Calling a tool that no handler answered returns an error result telling the plugin author to add a tool.call handler for the tool's full name, in the form mcp__<plugin>__<tool>.\n- The port is chosen at runtime and logged.\n- Behind the tengu_plugin_hooks_modules rollout flag.\n\n**Evidence**\n\n`loopback MCP server listening on 127.0.0.1:`\n\n- Area: Plugins\n- Tier: Under the hood\n- Useful: 2\/5\n- Signal: 3\/5"}