How to Use Claude With OpenClaw: Anthropic API Setup Guide [2026]

Claude by Anthropic is the most commonly used LLM with OpenClaw, and for good reason. Claude excels at tool use (function calling), which is the core mechanism OpenClaw uses to execute real-world actions like managing calendars, editing documents, and browsing the web. Claude also tends to follow complex multi-step instructions more reliably than alternatives.

This guide covers API key setup, model selection, cost optimization, and advanced configuration for getting the most out of Claude with OpenClaw.

Why Is Claude Recommended for OpenClaw?

OpenClaw relies heavily on the LLM's ability to use tools — reading databases, calling APIs, editing files, and making decisions about which actions to take. Claude's tool use implementation is consistently reliable across these scenarios.

• Reliable tool use — Claude correctly identifies which tools to call and formats arguments properly, even in complex multi-step workflows
• Long context window — Claude supports up to 200K tokens of context, important for processing large documents and maintaining conversation history
• Strong instruction following — Claude adheres closely to system prompts, critical for OpenClaw persona and workflow configurations
• Safety features — Claude's built-in safety training reduces the risk of unintended actions in autonomous agent scenarios

What Do You Need Before Starting?

• A running OpenClaw instance
• An Anthropic account at console.anthropic.com
• A payment method added to your Anthropic account (API access requires billing)

How Do You Configure Claude With OpenClaw?

Step 1 — Get your API key

Log in to console.anthropic.com, navigate to API Keys, and create a new key. Copy it immediately — you will not be able to see it again.

Step 2 — Add the key to OpenClaw config

llm:
  provider: "anthropic"
  model: "claude-sonnet-4-20250514"
  api_key: "sk-ant-api03-your-key-here"
  max_tokens: 4096
  temperature: 0.7

Step 3 — Set usage limits

In the Anthropic console, set a monthly spending limit to prevent unexpected costs:

# In Anthropic Console → Settings → Limits
# Set monthly limit: $50 (recommended starting point)
# Set per-minute rate limit as needed

Step 4 — Configure model routing (optional)

For cost optimization, route different tasks to different models:

llm:
  provider: "anthropic"
  default_model: "claude-sonnet-4-20250514"
  model_routing:
    complex_reasoning: "claude-opus-4-20250514"
    simple_tasks: "claude-haiku-3-5-20241022"
    code_generation: "claude-sonnet-4-20250514"

Step 5 — Start and verify

openclaw start

Send a test message through your configured messaging channel. Check the OpenClaw logs to confirm Claude API calls are succeeding.

Which Claude Model Should You Choose?

Our recommendation for most users: Start with Sonnet 4 as your default model. It handles 90% of typical OpenClaw tasks (calendar management, research, document editing) at a fraction of Opus cost. Switch to Opus only for tasks that genuinely require deeper reasoning.

How Do You Fix Common Claude API Issues?

• 401 Authentication error: Your API key is invalid or expired. Generate a new one in the Anthropic console. Make sure you are using the full key including the sk-ant-api03- prefix.
• 429 Rate limit exceeded: You are sending too many requests per minute. Reduce concurrent requests or upgrade your API tier in the Anthropic console.
• Overloaded error (529): Anthropic's servers are at capacity. OpenClaw automatically retries with exponential backoff. If persistent, switch to a less busy model (Haiku is rarely overloaded).
• High costs: Check your usage dashboard at console.anthropic.com. Common causes are long system prompts, excessive conversation history, or using Opus for simple tasks. Enable model routing to fix this.
• Tool use errors: If Claude is not calling tools correctly, check that your tool definitions are clear and have proper descriptions. Ambiguous tool names confuse the model.

FAQ

Which Claude model should I use with OpenClaw?

For most users, Claude Sonnet 4 is the best balance of quality and cost. Use Claude Opus 4 for complex reasoning, analysis, and tasks that require high accuracy. Use Claude Haiku for simple routing, classification, and high-volume low-complexity tasks.

How much does Claude API usage cost with OpenClaw?

Typical OpenClaw usage with Claude Sonnet runs $15-30 per month. Claude Opus costs roughly 5x more per token, so expect $40-80 per month for heavy Opus usage. You can mix models to optimize costs — use Haiku for simple tasks and Opus only for complex ones.

Can I switch between Claude and GPT without reconfiguring?

Yes. OpenClaw abstracts the LLM provider behind a unified interface. Change the provider and model in your config.yaml and restart. Your messaging channels, tools, and workflows stay the same.

Does OpenClaw support Claude's tool use feature?

Yes. OpenClaw natively supports Claude's tool use (function calling) capability. This is how OpenClaw executes actions like calendar management, web browsing, and file editing. Claude's tool use is generally more reliable than GPT's function calling for complex multi-step workflows.

*Last updated: March 2026. Published by the Remote OpenClaw team at remoteopenclaw.com.*