LLM Anthropic Plugin Adds Claude 5 Support and Server-Side Model Context Protocol Tools
Simon Willison updated the llm-anthropic plugin, adding support for Claude 5 models alongside server-side tools like WebSearch, WebFetch, CodeExecution, and AnthropicMCP. The update integrates with llm>=0.32 to stream reasoning traces, tool execution events, and simplified thinking effort controls directly in the command line.
Impact: Medium
Why it matters
Integrating server-side MCP tools directly into the CLI removes the friction of building custom loops, streamlining command-line workflows for advanced reasoning models.
TL;DR
- 01Adds support for Claude 5 models (fable-5, sonnet-5, opus-5).
- 02Enables server-side tool calling via the -T flag.
- 03Simplifies thinking effort configuration across five levels.
Key facts
- Supported Models
- claude-fable-5, claude-sonnet-5, claude-opus-5
- Dependency Requirement
- llm>=0.32
- Server-Side Tools
- WebSearch, WebFetch, CodeExecution, AnthropicMCP
- Thinking Effort Options
- low, medium, high, xhigh, max
Native Server-Side Tools and MCP Integration
The updated llm-anthropic plugin standardizes server-side tool invocations under the unified -T flag in the llm CLI. Developers can invoke WebSearch, WebFetch, CodeExecution, and AnthropicMCP directly without maintaining custom client-side execution loops. Server-side tool execution and reasoning events stream as typed events when paired with llm>=0.32.
Simplified Reasoning and Thinking Controls
Extended thinking configuration replaces options like thinking_budget, thinking_display, and thinking_adaptive with streamlined thinking and thinking_effort settings (low, medium, high, xhigh, max). For claude-sonnet-5 and claude-opus-5, thinking can be toggled off via -o thinking 0, while claude-fable-5 keeps thinking enabled permanently. Use -R or --hide-reasoning to suppress reasoning tokens from standard output and logging streams.
Try it in 2 minutes
llm -m claude-sonnet-5 -T WebSearch "Latest AI developments"bash
✓ When to use
- When running Claude 5 models and requiring server-side tool use via the LLM command line tool.
✕ When NOT to use
- When you are using older versions of the LLM CLI below 0.32 without updating.
What to do today
- Upgrade your llm package to version 0.32 or newer.
- Use the -T flag to trigger server-side tools like WebSearch or CodeExecution.
Sources