New features / v2.1.280
Configure the MCP description length cap
CHANGELOG · original
Added CLAUDE_CODE_MAX_MCP_DESCRIPTION_LENGTH to change the 2,048-character cap on MCP tool descriptions and server instructions for every MCP server in the session Open official changelog ↗ Documentation
Documentation excerpt
For MCP server authors
If you're building an MCP server, the server instructions field becomes more useful with tool search enabled. Server instructions help Claude understand when to search for your tools, similar to how skills work.
Add clear, descriptive server instructions that explain:
- What category of tasks your tools handle
- When Claude should search for your tools
- Key capabilities your server provides
Claude Code truncates each tool description and each server's instructions at 2,048 characters by default. Keep them concise, and put critical details near the start.
To change the limit for every MCP server in your session, set CLAUDE_CODE_MAX_MCP_DESCRIPTION_LENGTH to a number of characters. This variable requires Claude Code v2.1.280 or later.
Documentation snapshot · 2026-09-23