5.2 — Technical Fundamentals

CCDV-F Domain 5 · Task 5.2

What You Need to Know

A Claude application talks to the API over HTTP with JSON. Official SDKs wrap the wire in seven languages (Python, TypeScript, C#, Go, Java, PHP, Ruby) plus the ant CLI.

What the SDK Wraps

• Credential resolution and anthropic-version header
• Typed request construction and typed responses
• Typed exception hierarchy mapped from status codes
• Automatic retry of the transient class with backoff; default timeout 10 minutes
• SSE parsed into typed events
• Request id exposed as _request_id
• Auto-pagination over list endpoints

Exception Classes (most-specific-first)

Status	Exception
400	BadRequestError
401	AuthenticationError
403	PermissionDeniedError
404	NotFoundError
409	ConflictError
422	UnprocessableEntityError
429	RateLimitError
≥500	InternalServerError
transport	APIConnectionError

Branch on the exception class, never on the message text. Spend-cap 429 has error_code enforced_spend_limit_reached and no retry-after — do not retry.

Retry and Timeout Defaults

Certain errors retried 2 times by default with exponential backoff. Default timeout 10 minutes. Worst-case wall-clock ≈ timeout × attempts. Set both on purpose at one layer. Your own three-attempt loop on top of defaults multiplies attempts and re-sends deterministic failures.

Pagination

List endpoints return pages. Request takes limit + optional after_id/before_id. Response carries data, has_more, first_id, last_id. Page size defaults to 20, tops out at 1,000. SDK auto-paginates on iteration.

What the SDK Does Not Change

Same models, same pricing, same rate limits. No service-level guarantee. Does not manage your context window, prompt or cost.

Escape Hatches (without dropping the SDK)

• .with_raw_response / .with_streaming_response for headers and status
• ANTHROPIC_LOG=debug for traffic (keep out of production)
• extra_body / extra_query / extra_headers for fields types lag
• client.get / client.post for unwrapped endpoints
• client.beta with betas list for beta features

Transports

Three shapes: plain request/response (code consumer), streaming SSE (person watching), websocket (bidirectional). Choose by the consumer, not by preference.