Claude Code Was Billing Tens of Thousands of Hidden Tokens Per Turn

Every Claude Code message carries invisible weight: tool definitions, skill catalogs, system instructions for features you never touch. Easy to ignore. Hard to ignore once you see tens of thousands of tokens charged every turn.

TypeScript educator Matt Pocock published a practical way to measure and cut that overhead. (source)

/context shows the hidden bill

In a session, /context breaks window usage into categories:

• system prompt
• tools (usually the largest bucket)
• MCP tool definitions
• memory (CLAUDE.md and rules)

Unused tools still ship their full schemas every turn. /context alone does not rank individual tools by size; a small logging proxy (proxy.mjs) can surface per-tool byte ranking when you need the long tail.

Two settings.json levers remove most of it

Disable flags turn off whole feature bundles:

• disableBundledSkills — drops bundled skills such as dataviz, review, init
• disableWorkflows — removes the Workflow tool (often the single biggest tool)
• disableRemoteControl — drops remote-control tools

permissions.deny removes specific tools by bare name:

• EnterPlanMode, ExitPlanMode if you do not use plan mode
• DesignSync if you do not use design tools
• NotebookEdit if you never touch notebooks
• SendMessage, PushNotification if you do not want notification tools
• CronCreate if you do not schedule work

Put these in ~/.claude/settings.json (global) or .claude/settings.json (project).

One deny trap

A bare name like "NotebookEdit" strips the tool definition from the payload. A scoped rule like "Bash(rm *)" only blocks invocation and still sends the definition. If the goal is tokens, deny by name only.

Do not disable tools you actually use. Keep plan-mode tools if you live in plan mode; keep notebook tools if you edit notebooks.

Optimize the system surface before the code

Restart Claude Code, run /context again, and confirm tool count and total tokens dropped. That delta is what you save every turn.

Long sessions already squeeze the window. Clean settings.json before you micro-optimize application code. It takes about a minute.