Anthropic Common Errors Overview Every Anthropic API error includes a field and HTTP status code. Here are the real errors you'll hit and how to fix them. Error Reference Instructions Step 1: (401) Cause: API key is missing, malformed, or revoked. Fix: --- Step 2: (429) Cause: Exceeded requests per minute (RPM) or tokens per minute (TPM). Fix: Rate limit tiers (as of 2025): | Tier | RPM | TPM (input) | TPM (output) | |------|-----|-------------|--------------| | Tier 1 (free) | 50 | 40,000 | 8,000 | | Tier 2 ($40+) | 1,000 | 80,000 | 16,000 | | Tier 3 ($200+) | 2,000 | 160,000 | 32,000 | | Ti…