Anthropic Messages Integration

Anthropic Messages style interface is suitable for Claude Code, some Anthropic SDKs, or tools that only support Anthropic API format.

Interface Information

Configuration	Value
Base URL	https://api.corerouter.cloud
Endpoint	https://api.corerouter.cloud/v1/messages
API Key Header	Authorization: Bearer sk-... or x-api-key: sk-...
Version Header	anthropic-version: 2023-06-01
Required Fields	model, max_tokens, messages

Claude Code's ANTHROPIC_BASE_URL typically fills https://api.corerouter.cloud; don't fill to /v1/messages.

curl Example

export COREROUTER_API_KEY="sk-xxxxxxxxxxxxxxxx"

curl https://api.corerouter.cloud/v1/messages \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $COREROUTER_API_KEY" \
  -H "anthropic-version: 2023-06-01" \
  -d '{
    "model": "claude-sonnet-4-5",
    "max_tokens": 1024,
    "messages": [
      {
        "role": "user",
        "content": "Hello, please introduce yourself."
      }
    ]
  }'

Using x-api-key

If your client only supports Anthropic's native x-api-key Header, test like this:

curl https://api.corerouter.cloud/v1/messages \
  -H "Content-Type: application/json" \
  -H "x-api-key: $COREROUTER_API_KEY" \
  -H "anthropic-version: 2023-06-01" \
  -d '{
    "model": "claude-sonnet-4-5",
    "max_tokens": 1024,
    "messages": [
      {"role": "user", "content": "Hello"}
    ]
  }'

Streaming Output

curl https://api.corerouter.cloud/v1/messages \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $COREROUTER_API_KEY" \
  -H "anthropic-version: 2023-06-01" \
  -d '{
    "model": "claude-sonnet-4-5",
    "max_tokens": 1024,
    "stream": true,
    "messages": [
      {"role": "user", "content": "Introduce CoreRouter in three sentences."}
    ]
  }'

System Prompt

curl https://api.corerouter.cloud/v1/messages \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $COREROUTER_API_KEY" \
  -H "anthropic-version: 2023-06-01" \
  -d '{
    "model": "claude-sonnet-4-5",
    "max_tokens": 1024,
    "system": "You are a professional, concise technical documentation assistant.",
    "messages": [
      {"role": "user", "content": "Write an API Key security reminder."}
    ]
  }'

Common Issues

• Claude Code connection failure: Confirm environment variable Base URL doesn't include /v1.
• max_tokens error: Anthropic Messages typically requires explicit max_tokens.
• Header incompatibility: Use Authorization: Bearer ... first; if client only uses x-api-key, then use x-api-key.
• Tool calling unstable: Select models marked as supporting Tool Use / Coding Agent in console.