Choosing a Claude Model
The Opus/Sonnet/Haiku tradeoff and how to pick — without guessing.
Tokens, Context & Pricing
Count tokens correctly, max_tokens vs context window, and estimating cost.
Your First API Call
Install the SDK, authenticate, and make a real call to Claude in Python, TypeScript, or cURL.
Streaming & Multi-Turn Conversations
Stream responses and manage history on a stateless API.
Tool Use / Function Calling
Define tools, run the agentic loop, and handle results.
Vision, PDF & File Input
Send images and documents, and reuse uploads by file_id.
Structured Output
Get schema-conforming JSON you can rely on — not prompt-and-pray.
Extended Thinking & Effort
Adaptive reasoning and the effort control — choosing depth by workload.
Effort tuning: 5 levels, model defaults, and the cache trap
The July 2026 effort parameter has five levels — low, medium, high, xhigh, max — and lives inside output_config, not at the top level. It affects tool calls (not just thinking), invalidates prompt cache when changed mid-conversation, and each model has a different recommended starting point. The practical tuning guide.
The advisor tool: Sonnet does the work, Fable does the thinking
The advisor server-tool (beta advisor-tool-2026-03-01) lets a fast executor model consult a stronger model mid-turn. Full field reference, the token-accounting trap most integrators miss, the model pairing matrix, and the exact prompts Anthropic ships in production.
Prompt Caching & Cost Optimization
Reuse a stable prompt prefix to cut cost and latency — and the gotcha that breaks it.
Mid-Conversation System Messages
Steer a long agent session without blowing up the prompt cache — the new system role you can append after any user turn.
Mid-Conversation Tool Changes
Add and retire tools between turns without invalidating the prompt cache — the Opus 5 beta that fixes the biggest hidden tax on long agent sessions.
Building Agents on the API
Single call vs workflow vs custom agent — the decision test and loop design.
Managed Agents
Anthropic-hosted agent loop: agents vs sessions, environments, memory, vaults, and scheduled deployments (cron).
Managed Agents Memory Stores
The July 2026 beta — server-side persistent memory that mounts into a Managed Agents sandbox, with versioning, audit trail, and redaction.
Cowork & Agent Teams
The agentic desktop workspace and multi-agent collaboration as products.
MCP & Connecting to Tools
Call remote MCP servers straight from the Messages API — the request shape, allowlists and denylists, deferred loading, and the limits that bite in production.
MCP 2026-07-28: The Stateless Spec
The biggest MCP revision since launch: the session is gone, every request self-describes, and any server instance can answer any call. What actually changed on July 28, 2026, and how to migrate without breaking today's servers.
MCP Apps: Interactive UIs Inside a Tool Call
MCP Apps (SEP-1865) lets an MCP server ship an HTML UI that the client renders inside a sandboxed iframe — with every action still routed through the standard JSON-RPC audit path. What the spec actually says, what to build with it, and what to refuse to build.
MCP Tasks: Long-Running Work Without the Session
The 2026-07-28 stateless MCP spec killed the session — so how do you model a 20-minute CI job, a batch import, or a human approval gate? With the official Tasks extension (SEP-2663). Full lifecycle, wire protocol, migration from the old experimental Tasks API, and the polling/notification patterns that actually work in production.
Playwright MCP: The Deep Practical Guide (2026)
Microsoft's Playwright MCP is now the #1 MCP server in the world — ahead of GitHub and Figma. The bit almost nobody teaches: the default accessibility-snapshot mode is not just faster than vision, it's a completely different automation paradigm. Profiles, opt-in caps, browser-extension mode that attaches to your real Chrome, the token-cost fight against Playwright-as-a-Skill, and the security line you must not cross.
Safety, Refusals & Fallbacks
Handle refusals gracefully and distinguish them from classifier blocks.
Server-Side Fallbacks & Fallback Credit
The Opus 5 beta that turns a Fable 5 / Opus 5 refusal into a normal answer inside one API call — plus the credit token that stops you from paying the prompt cache twice on the retry.
Errors, Rate Limits & Reliability
The error map, retries with backoff, rate-limit tiers, and model migration.
Memory & Context Editing
Give agents persistent memory and auto-pruned context — the client-side memory tool plus context editing that clears stale tool results to survive long runs.
Programmatic Tool Calling
Let Claude call your tools from Python inside the code-execution sandbox — cutting round-trips and keeping intermediate results out of context.
The Admin API: automate your Claude org
The operator's guide to Anthropic's Admin API — list members, invite users, run RBAC groups, offboard cleanly. Console + Claude Enterprise, with the seat-pool and SSO gotchas that trip real teams.
Inference Hooks: inline DLP for Claude Enterprise
The operator's guide to Claude Enterprise Inference Hooks — the HTTPS webhook that lets your DLP server allow or deny every prompt across chat, Claude Code, and Cowork, before the model sees it. Full spec, verdict schema, signing, rollout playbook.