castiel

MCP servers ​

castiel connects to Model Context Protocol servers to give the agent tools beyond the built-in set. A headless browser, proxy access, anything an MCP server speaks.

Declaring servers ​

MCP servers are declared in the mcp.json configuration file. castiel watches the file and reloads it automatically. Edit it while castiel is running and the servers come up or drop without a restart.

How MCP tools behave ​

  • Each connected server appears in Settings → MCP Servers with its own on/off switch; its tools are not part of the built-in tool catalog.
  • Every MCP tool unlocks with Reconnaissance (phase 2), because they are arbitrary target-interactive tools. See Engagement phases.
  • MCP tools stack on top of the built-in toolset; the agent sees them alongside the harness tools.

castiel highly recommends obscura for headless browser tooling, but the choice is yours.