Anthropic rolled out MCP Tool Search for Claude Code on January 15th. The feature targets a specific problem: MCP servers with 50+ tools consuming enormous chunks of context before you've even asked a question.
The actual problem
So MCP has gotten popular. More popular than the protocol's original design probably anticipated. Users on GitHub were documenting setups with 7+ servers consuming 67,000+ tokens just in tool descriptions. That's before any actual work happens.
The fix is pretty straightforward. Claude Code now detects when MCP tool descriptions would eat more than 10% of your context. When that threshold hits, tools load via search instead of preloading everything upfront.
Otherwise, MCP works exactly as before.
If you're building MCP servers
Mostly nothing changes. But the "server instructions" field becomes more useful now. It helps Claude know when to search for your tools. Similar to how skills work, apparently.
For client developers
Anthropic wants you implementing the ToolSearchTool. The docs are up. They built it with a custom search function for Claude Code specifically.
What they didn't ship
There's a paragraph in the announcement about programmatic tool calling, composing MCP tools via code. They experimented with it. They're not shipping it.
The reasoning: context reduction was the more urgent problem. Make of that what you will.
