MCP Lens

MCP context accounting for AI coding clients. MCP Lens automatically collects MCP tool usage from Claude Code, Codex, and Gemini CLI, then shows you what each server and tool actually costs versus how often you use it.

What it does

• Status bar — a live summary of recent MCP calls and the tokens you saved.
• Sidebar — an activity-bar view with a client ▸ server ▸ tool tree, each tool tagged with a keep / inspect / remove recommendation.
• Report — run MCP Lens: Show Report for a per-client Markdown breakdown of calls, response tokens, definition tokens, and recommendations.

Zero config

Just install and go. MCP Lens auto-detects which clients are installed, reads their logs (read-only), and backfills past sessions on startup. There is nothing to set up and no account required.

Settings

• mcpLens.reportDays (default 30) — how many days the status summary and report aggregate. Original client logs expire after ~30 days, but the Lens database keeps history permanently, so longer windows still work.

Definition tokens

Response-token accounting works out of the box. To also measure how many tokens each tool's definition costs (its schema, injected into every prompt), run:

npx mcp-lens scan

This probes your configured MCP servers and records definition token counts, which then appear in the report and sidebar recommendations.