[Bug] MCP tools consume excessive context on fresh initialization (14% of window)

Bug Description
All MCP tools are loaded automatically on fresh context using up 14% of the context window.

Environment Info

• Platform: darwin
• Terminal: ghostty
• Version: 2.1.105
• Feedback ID: bf1c4938-b624-473b-bb4f-a7898a9d979a

Problem

The official MCP docs state that Tool Search is enabled by default and MCP tools should be deferred and loaded on demand. In practice, Tool Search never activates — all MCP tools are loaded eagerly at session start, consuming ~30k tokens (15% of the 200k context window).

Debug evidence

The debug log shows:

[ToolSearch:optimistic] mode=standard, ENABLE_TOOL_SEARCH=undefined, result=false

After explicitly setting the env var:

[ToolSearch:optimistic] mode=standard, ENABLE_TOOL_SEARCH=true, result=false

The env var is read correctly but result is still false. All 21 MCP servers (1 local + 19 claude.ai marketplace + 1 project-level) connect eagerly at startup and inject their full tool schemas into context.

What I tried

1. Default (no env var) — result=false
2. export ENABLE_TOOL_SEARCH=true — still result=false

Expected behavior

Per the docs at https://code.claude.com/docs/en/mcp:

Tool search is enabled by default. MCP tools are deferred rather than loaded into context upfront, and Claude uses a search tool to discover relevant ones when a task needs them.