Tool Search and working smart
How Claude Code stays fast with dozens of MCP servers
⏱ Est. ~4 min
01 · Read
Here's a problem you wouldn't see coming: the more MCP servers you add, the slower Claude gets.
Why? Every MCP server exposes tools — and every tool has a description Claude has to read. If you have 10 servers with 15 tools each, that's 150 tool descriptions loaded into Claude's context window before you even ask a question. That eats up space for the actual conversation.
It's like trying to have a meeting where everyone has to read everyone's full resume before you can discuss the project.
Key points
- Every MCP tool has a description that consumes context tokens
- More servers = more tool descriptions = less room for conversation
- 10+ servers can eat a significant chunk of context
- This is the problem Tool Search solves
02 · Read
Tool Search is Claude Code's solution. Instead of preloading every tool from every server, it defers them. When you ask a question, Claude uses a search tool to find which MCP tools are relevant, loads only those, and moves on.
It's automatic — you don't configure it. Tool Search kicks in when your MCP tool descriptions would consume more than 10% of the context window.
The result? You can connect dozens of MCP servers without wasting context on tools you're not using.
Key points
- Tool Search loads MCP tools on demand, not upfront
- Auto-enabled when tools exceed 10% of context
- Only loads tools Claude actually needs for the current task
- Lets you run lots of MCP servers with no performance cost
03 · Code example
Tool Search is on by default, but you can tune it. The ENABLE_TOOL_SEARCH environment variable controls its behavior.
Default (auto — kicks in at 10% context usage)
claude
Custom threshold (kicks in at 5%)
ENABLE_TOOL_SEARCH=auto:5 claude
Fully disabled (all tools preloaded)
ENABLE_TOOL_SEARCH=false claude
Most users don't need to change this — the default auto mode works well. Lower the threshold if you have lots of servers. Only disable if you're debugging a tool discovery issue.
04 · Read
Inside Claude Code, the /mcp command is your control panel for MCP servers. Type /mcp to see every connected server and its status.
Green means connected; if a server needs authentication (like GitHub or Sentry), /mcp walks you through OAuth login — it opens a browser, you log in, and Claude gets access.
You can also clear authentication, view errors, and see which tools each server provides. Think of /mcp as the dashboard for all your MCP connections.
Key points
- /mcp shows all servers and connection status
- Use it to authenticate with OAuth servers (GitHub, Sentry, etc.)
- "Clear authentication" resets access when needed
- First place to check when an MCP server isn't working
05 · Quiz
You've configured 20 MCP servers, and Claude feels slow. Which feature automatically reduces context usage by loading tools on demand?
- MCP caching
- Server batching
- Tool Search
- Context compression
06 · Fill in the blank
Inside Claude Code, type /_____ to see the status of all MCP servers and authenticate with OAuth services.
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※ This is an independent Traditional Chinese teaching project — not an official Anthropic product. Claude™ is a trademark of Anthropic, PBC.