Engineering simulation is file-based, scriptable, local, artifact-heavy, and long-running. CAE agents work with solver executables, model files, Python/Java/journal scripts, shell commands, logs, checkpoints, and plots — a CLI command surface composes with all of that and matches how Codex CLI, Claude Code, and other coding agents already operate.
MCP is useful for API-style integrations and remote tool discovery, but a broad MCP surface adds context overhead and wrapper maintenance. For COMSOL, Abaqus, Ansys Workbench, OpenFOAM, LTspice, and similar solvers, sim-cli keeps the source of truth as a small, auditable command loop.
The practical consequence: an agent learns the whole surface from one
sim --json describe call, and every command it runs is a line a human can
re-run, paste into a bug report, or drop into a shell script. See
agent-readability.md for the I/O contract that makes
this work.