Build HTTP Headers for an AI API Request

Every AI API request requires a specific set of HTTP headers: an Authorization header with the correct format for the provider, Content-Type set to application/json, and in some cases provider-specific headers like Anthropic's anthropic-version or OpenAI's OpenAI-Organization for team accounts. Getting headers wrong is one of the most common causes of 401 Unauthorized and 400 Bad Request errors when first integrating an AI API. The headers builder generates the complete header set for a given provider, with placeholders for your API key and optional fields clearly labelled. The Authorization header format differs by provider: OpenAI uses "Authorization: Bearer sk-..." while Anthropic uses "x-api-key: sk-ant-..." as a custom header rather than the standard Authorization header. Gemini uses an API key as a query parameter (key=...) rather than a header at all for REST requests, though the Python and JS SDKs handle this automatically. These differences trip up developers building provider-agnostic clients or switching between providers. This example generates headers for an Anthropic Claude API request, including the required anthropic-version header that specifies the API version date. Missing this header returns a 400 error with a message about the version being required — a confusing error for developers new to the Anthropic API who expect only an API key to be necessary.

Provider: Anthropic
API Key: sk-ant-api03-YOUR_KEY_HERE
Model: claude-3-5-sonnet-20241022
Stream: true
Beta features: tools, prompt-caching