CLI vs MCP: two surfaces
One browser engine exposed two ways — the human CLI and the agent-facing MCP server — and when to use each.
browserlane is one engine behind two surfaces. The same browser automation core is exposed as a human-facing CLI and as an MCP server for agents. They drive Chrome the same way; they differ only in how you talk to them.
The two surfaces
| CLI | MCP server | |
|---|---|---|
| Who uses it | People and shell scripts | AI agents |
| How you invoke it | bl <command> … | bl mcp (JSON-RPC 2.0 over stdio) |
| How you target work | You type commands | The agent calls tools from prompts |
The CLI is what you've seen throughout these docs: bl go, bl map,
bl click, and the rest. The MCP server, started with bl mcp, exposes
equivalent capability as a catalog of tools an agent can call — you register it
once with bl add-mcp (see Wire up an agent).
When to use which
Reach for the CLI when you're driving the browser yourself, scripting a repeatable task, wiring automation into CI, or prototyping a flow you'll later hand to an agent.
Reach for the MCP when an AI agent should drive the browser from natural-language instructions — exploring a page, filling a form, or extracting data as part of a larger agent task.
Because both surfaces share one engine, a flow you work out by hand on the CLI behaves the same when an agent runs it through the MCP.
The surfaces are not 1:1
The MCP tools cover the same engine, but they are not a one-to-one mirror of the CLI commands:
- Some verbs are renamed —
bl goisbrowser_navigateon the MCP side. - Some single commands split into get/set tool pairs —
bl viewportbecomesbrowser_get_viewportplusbrowser_set_viewport. - A few capabilities (like the page-clock controls) are MCP-only.
- The setup, daemon, and agent-wiring plumbing (
bl install,bl daemon,bl add-mcp) is CLI-only.
See the exact correspondence
The CLI ↔ MCP mapping lists how every bl
command lines up with the MCP tools, including the renames and the
CLI-only / MCP-only cases.
Related
- Wire up an agent (MCP).
- MCP reference — the full tool catalog.
bl mcpin the CLI reference.