Claude Code operates within a 200k token context window. Everything Claude needs to function — system prompt, tools, MCP servers, agents, memory files, skills, and your conversation — competes for that space. The /context command breaks down exactly how many tokens each component consumes, giving you full visibility into a resource that drains silently.
It's easy to overlook at first. You start adding MCP servers, custom agents, rules... and before you know it, a significant chunk of the context window is already pre-consumed before you type your first message. /context keeps you aware.
Result:
/context
Context Usage
claude-opus-4-5-20251101 · 51k/200k tokens (26%)
Estimated usage by category
System prompt: 2.6k tokens (1.3%)
System tools: 17.6k tokens (8.8%)
MCP tools: 907 tokens (0.5%)
Custom agents: 935 tokens (0.5%)
Memory files: 302 tokens (0.2%)
Skills: 61 tokens (0.0%)
Messages: 30.5k tokens (15.3%)
Free space: 114k (57.0%)
Autocompact buffer: 33k tokens (16.5%)
Setup
No setup needed. The command is available in any session.
1. Run the command
Type /context at any point during your session:
/context
2. Analyze the breakdown
The output shows consumption per category. Pay close attention to:
- System tools and MCP tools: tool definitions load on every request. A few MCP servers can consume a significant percentage.
- Free space: your actual working space. This is what's left for messages, file reads, and command outputs.
- Autocompact buffer: a reserve Claude uses for automatic compaction when context fills up.
3. Act on what you see
If MCP tools consume too much, run /mcp to see per-server costs and disable those you don't need in this session. If free space drops below 30%, consider using /compact or starting a fresh session.
Reference
| Category | What it includes |
|---|---|
| System prompt | Claude Code's internal instructions |
| System tools | Built-in tools (Read, Edit, Bash, Grep, Glob, etc.) |
| MCP tools | Tool definitions from connected MCP servers |
| Custom agents | Custom agents defined in .claude/agents/ |
| Memory files | CLAUDE.md and auto memory files |
| Skills | Descriptions of registered skills |
| Messages | Your conversation: prompts, responses, and tool results |
| Free space | Tokens available to keep working |
| Autocompact buffer | Reserve for automatic compaction (~16.5%) |
Official docs: The context window