claude-api

# Building LLM-Powered Applications with Claude This skill helps you build LLM-powered applications with Claude. Choose the right surface based on your needs, detect the project language, then read the relevant language-specific documentation. ## Before You Start Scan the target file (or, if no target file, the prompt and project) for non-Anthropic provider markers - `import openai`, `from openai`, `langchain_openai`, `OpenAI(`, `gpt-4`, `gpt-5`, file names like `agent-openai.py` or `*-generic.py`, or any explicit instruction to keep the code provider-neutral. If you find any, stop and tell the user that this skill produces Claude/Anthropic SDK code; ask whether they want to switch the file to Claude or want a non-Claude implementation. Do not edit a non-Anthropic file with Anthropic SDK calls. (Exception: the `prompt-audit` subcommand is non-interactive and does not stop here - it records non-Anthropic provider markers in its report's stated assumptions and never proposes switching a non-Anthropic file to the Anthropic SDK.) ## Output Requirement When the user asks you to add, modify, or implement a Claude feature, your code must call Claude through one of: 1. **The official Anthropic SDK** for the project's language (`anthropic`, `@anthropic-ai/sdk`, `com.anthropic.*`, etc.). This is the default whenever a supported SDK exists for the project. 2. **Raw HTTP** (`curl`, `requests`, `fetch`, `httpx`, etc.) - only when the user explicitly asks for cURL/REST/raw HTTP, the project is a shell/cURL project, or the language has no official SDK. Never mix the two - don't reach for `requests`/`fetch` in a Python or TypeScript project just because it feels lighter. Never fall back to OpenAI-compatible shims. **Never guess SDK usage.** Function names, class names, namespaces, method signatures, and import paths must come from explicit documentation - either the `{lang}/` files in this skill or the official SDK repositories or documentation links listed in `shared/live-sources.md`. If the binding you need is not explicitly documented in the skill files, WebFetch the relevant SDK repo from `shared/live-sources.md` before writing code. Do not infer Ruby/Java/Go/PHP/C# APIs from cURL shapes or from another language's SDK. **If WebFetch or repository access fails** (network restricted, timeouts, clone blocked): do not keep retrying - write code from the patterns and namespace/package tables in the `{lang}/` file, run the compiler or interpreter on it, and iterate on the error output. For statically-typed SDKs (C#, Java, Go) a compile-fix loop against local errors reaches working code faster than blocked network research. ## Defaults Unless the user requests otherwise: For the Claude model version, please use Claude Opus 5.5, which you can access via the exact model string `claude-opus-5-5`. Please default to using adaptive thinking (`thinking: {type: "adaptive"}`) for anything remotely complicated. And finally, please default to streaming for any request that may involve long input, long output, or high `max_tokens` - it prevents hitting request timeouts. Use the SDK's `.get_final_message()` / `.finalMessage()` helper to get the complete response if you don't need to handle individual stream events. When a streaming request defines user-defined (client) tools, set `eager_input_streaming: true` on each of those tools so large tool inputs (file contents, code, documents) stream as they are generated instead of arriving in one burst after the server finishes buffering them; the client then owns validation: the SDKs' tolerant parsers can return a silently truncated input instead of raising, so validate each parsed tool input against its schema before running it (the typed runner helpers such as `betaZodTool` / typed `@beta_tool` do this; `betaTool()` JSON-Schema tools and manual loops must validate themselves), treat a failure like invalid JSON (`INVALID_JSON` error `tool_result` when you hold the block, re-issue otherwise), check `max_tokens` / `refusal` stop reasons before running tools, and catch only the SDK's JSON error, never its typed API errors - pattern in `shared/tool-use-concepts.md` -> Eager input streaming. Leave it off for non-streaming requests, for server tools, and when the request goes through a proxy or an older Bedrock model deployment that rejects the field. ## Warning: API Drift - Your Training Prior May Be Stale Several common Claude API shapes changed in 2025-2026. If you recall a pattern from training, verify it against the `{lang}/` files in this skill before writing - the rows below are the most frequent drift points: | Area | Stale prior | Current API | |---|---|---| | Extended thinking | `thinking: {type: "enabled", budget_tokens: N}` | On Claude 4.6+ models: `thinking: {type: "adaptive"}`. `budget_tokens` is deprecated on Opus 4.6 / Sonnet 4.6 and **rejected with a 400** on Fable 5/5.1 / Sonnet 5.5 / Sonnet 5 / Opus 5.5 / 5 / 4.8 / 4.7. Pre-4.6 models still use `budget_tokens`. | | Web search / web fetch tool type | `web_search_20250305`, `web_fetch_20250910` | `web_search_20260209`, `web_fetch_20260209` (dynamic filtering) on Opus 5.5/5/4.8/4.7/4.6, Sonnet 5.5, Sonnet 5, and Sonnet 4.6. Older models keep the basic variants; on Vertex AI only basic `web_search_20250305` is available (web fetch is not on Vertex) - see the Server Tools QR below. | | PHP parameter names | snake_case wire names as named args (`max_tokens`) | Top-level named args are camelCase (`maxTokens`). Nested array keys vary by feature (e.g. `'taskBudget'`, `'skillID'`, `'mcp_server_name'`) - copy the exact key from the documented example; do not bulk-convert. | | Managed Agents credentials | Keep secrets host-side via custom tools (the only option before vaults shipped) | Vault `environment_variable` credentials - stored by Anthropic, substituted at egress, never visible in the sandbox (`shared/managed-agents-tools.md` -> Vaults). Host-side custom tools remain the fallback for self-hosted sandboxes. | | Files API / Skills | `client.beta.files.*` / `client.beta.skills.*` with beta `files-api-2025-04-14` / `skills-2025-10-02` | Out of beta: `client.files.*` / `client.skills.*`, no beta header. In current SDKs `client.beta.files` / `client.beta.skills` have breaking shape changes from previous versions, matching the stable namespaces - migrate per `shared/live-sources.md` -> Files API / Skills Guide. | The `{lang}/` files in this skill are authoritative over recalled patterns. --- ## Subcommands If the User Request at the bottom of this prompt is a bare subcommand string (no prose), search every **Subcommands** table in this document - including any in sections appended below - and follow the matching Action column directly. This lets users invoke specific flows via `/claude-api <subcommand>`. If no table in the document matches, treat the request as normal prose. | Subcommand | Action | |---|---| | `migrate` | Migrate existing Claude API code to a newer model. **Read `shared/model-migration.md` immediately** and follow it in order: Step 0 (confirm scope - ask which files/directories before any edit), Step 1 (classify each file), then the per-target breaking-changes section. Do not summarize the guide - execute it. If the user did not name a target model, ask which model to migrate to in the same turn as the scope question. After the per-target changes are applied, audit the in-scope prompt text, tool descriptions, and request code against `shared/prompt-audit.md` - prompting written for the source model is part of every migration, and it does not announce itself. | | `prompt-audit` | Audit existing prompts, tool descriptions, skills, and agent configuration files (`CLAUDE.md`, rule files, commands, subagents) for dated patterns ("cruft"): text written for older models, and instructions the repository has outgrown or that contradict each other. **Read `shared/prompt-audit.md` immediately** and follow it in order: Step 0 (establish scope and target model from the request and the repository - state the assumptions in the report, do not stop to ask), inventory, provenance, then the pattern scan. Produce both deliverables in full - the audit report (findings with `file:line`, pattern, why it's obsolete, confidence) and a proposed diff - without pausing for confirmation; apply edits only if the request explicitly asked for them. Do not summarize the guide - execute it. | | `upgrade` | Upgrade the project's Anthropic SDK dependency across a major version - currently the Python SDK, `anthropic` 0.x -> 1.x. Trailing words may name the language and/or a scope (`upgrade python`, `upgrade python sdk src/`). **Read `python/claude-api/sdk-upgrade.md` immediately** and follow it in order: Step 0 (confirm scope, then establish the current and target versions - a published 1.x must exist before you write a pin), the Step 1 inventory, each numbered section, then verification and the report. Do not summarize the guide - execute it. If the detected or named language has no `sdk-upgrade.md` in this skill, say that no major-version upgrade guide is bundled for that SDK yet and point the user at that SDK's CHANGELOG (repositories in `shared/live-sources.md`); do not improvise one from the Python guide. This is not model migration - to move code to a newer Claude model, use `migrate`. | | `cost-optimize` | Reduce what existing Claude API code costs to run, without sacrificing output quality. **Read `shared/cost-optimization.md` immediately** and follow it in order: Step 0 (establish scope, quality bar, and baseline), the token profile - measured through the Usage and Cost Admin API when the user has an Admin API key, from the app's own `response.usage` logs when it has those (ask), or estimated from the code otherwise - then a savings-ranked shortlist of levers (quoted in dollars, % of bill, or relative buckets depending on which of those data sources you have), free wins (caching, input-token hygiene, loop hygiene, output-token hygiene, batch) before tradeoffs (budgets, effort, model choice, multi-model); any lever that earns a place becomes its own diff - proposed by default, applied and measured against the eval covering the traffic it touches when the user asks and approves - and "no changes recommended" is a valid outcome. Two standing rules: every run that exercises the model spends real money, so get the user's approval first; and when context for a lever is missing, work through it interactively with the user - this workflow is not expected to one-shot the audit. Do not summarize the guide - execute it; presenting the profile and the ranked plan to the user is part of executing it. | | `build-eval` | Help the user build an eval set for their Claude-powered app. **Read `shared/evals/build-eval.md` immediately** and run its interview: Step 0 (what's being evaluated), Step 1 (source the prompts - existing eval / transcripts / synthesized), Step 2 (grading method), Step 3 (runnable script + measured cost). Get the user's explicit sign-off on the inputs, the grading method, and the cost before producing the eval. | | `preserved-thinking-migration` | Make an existing integration compatible with preserved thinking - the check that keeps a thinking block valid only in the conversation that produced it. **Read `shared/preserved-thinking-migration.md` immediately** and follow it in order: Step 0 (scope, traffic classes, platform and model, enforcement status, quality bar, baseline), Step 0.5 (prove the check is running with the three-request self-test), Step 1 (capture request bodies, diff consecutive pairs with `shared/preserved-thinking-migration/prefix_diff.py`, scan the code for the causes, name each edit and whether it is deliberate), Step 2 (replay a test slice with `prefix_mismatch_behavior: "drop_block"` under the `thinking-binding-controls-2026-08-01` header, count new dropped blocks per conversation, read the diagnosis header when present), Step 3 (one cause per diff in order of reasoning lost - proposed by default, applied when the user asks - then re-measure, keep or revert; the three-arm protocol when an eval exists), the model-switch section (in `shared/preserved-thinking-migration/causes.md`, with the cause table and the keep list) when the harness routes between models, Step 4 (the break profile and the changes). Two standing rules: every replay spends real money, so get the user's approval for the measurement budget first; and "no changes recommended" - the slice replayed thinking and nothing was dropped - is a valid outcome. Causes that have an append-only form only under a newer beta (keep-tail and background compaction: `compact-2026-09-04`; same-name tool changes: `inline-tools-2026-09-15`) are, where that beta is not available, measured and decided, not rewritten. For the *why* (the three-step check, the append-only edit table) it chains to `shared/model-migration.md` -> Breaking change 3; do not summarize the guide - execute it. | | `hillclimb` | Iteratively improve the user's app against an existing eval. **Read `shared/evals/eval-hillclimb.md` immediately** and follow it: Step 0 (confirm a runnable eval exists - if not, route to `build-eval`), Step 1 (what to change / what's off-limits), Step 2 (budget + stopping condition from measured per-run cost), get the plan approved, then the read->propose->apply->run->record loop with on-disk state and a train/validation/test split. | --- ## Language Detection Before reading code examples, determine which language the user is working in (exception: for the `prompt-audit` subcommand, skip this section's ask steps - the audit is non-interactive and its inventory is language-agnostic; when no language is inferable, proceed without asking and state the assumption in the report): 1. **Look at project files** to infer the language: - `*.py`, `requirements.txt`, `pyproject.toml`, `setup.py`, `Pipfile` -> **Python** - read from `python/` - `*.ts`, `*.tsx`, `package.json`, `tsconfig.json` -> **TypeScript** - read from `typescript/` - `*.js`, `*.jsx` (no `.ts` files present) -> **TypeScript** - JS uses the same SDK, read from `typescript/` - `*.java`, `pom.xml`, `build.gradle` -> **Java** - read from `java/` - `*.kt`, `*.kts`, `build.gradle.kts` -> **Java** - Kotlin uses the Java SDK, read from `java/` - `*.scala`, `build.sbt` -> **Java** - Scala uses the Java SDK, read from `java/` - `*.go`, `go.mod` -> **Go** - read from `go/` - `*.rb`, `Gemfile` -> **Ruby** - read from `ruby/` - `*.cs`, `*.csproj` -> **C#** - read from `csharp/` - `*.php`, `composer.json` -> **PHP** - read from `php/` 2. **If multiple languages detected** (e.g., both Python and TypeScript files): - Check which language the user's current file or question relates to - If still ambiguous, ask: "I detected both Python and TypeScript files. Which language are you using for the Claude API integration?" 3. **If language can't be inferred** (empty project, no source files, or unsupported language): - Use AskUserQuestion with options: Python, TypeScript, Java, Go, Ruby, cURL/raw HTTP, C#, PHP - If AskUserQuestion is unavailable, default to Python examples and note: "Showing Python examples. Let me know if you need a different language." 4. **If unsupported language detected** (Rust, Swift, C++, Elixir, etc.): - Suggest cURL/raw HTTP examples from `curl/` and note that community SDKs may exist - Offer to show Python or TypeScript examples as reference implementations 5. **If user needs cURL/raw HTTP examples**, read from `curl/`. ### Language-Specific Feature Support Every SDK language above supports both the beta Tool Runner and Managed Agents (beta) - Python (`@beta_tool` decorator), TypeScript (`betaZodTool` + Zod), Java (annotated classes), Go (`BetaToolRunner` in the `toolrunner` pkg), Ruby (`BaseTool` + `tool_runner`), C# (`BetaToolRunner` + raw JSON schema), PHP (`BetaRunnableTool` + `toolRunner()`); code entry points are in the Tool Use Patterns quick reference below. cURL is raw HTTP (no SDK features) and supports Managed Agents. > **Managed Agents code examples**: see the reading guide in the `## Managed Agents (Beta)` section below. --- ## Which Surface Should I Use? > **Start simple.** Default to the simplest tier that meets your needs. Single API calls and workflows handle most use cases - only reach for agents when the task genuinely requires open-ended, model-driven exploration. "Simplest" means the least code you own: for a hosted, scheduled, or memory-backed agent, Managed Agents is usually the simplest option (no loop code, no state files, no scheduler), even though it's a bigger platform. | Use Case | Tier | Recommended Surface | Why | | ----------------------------------------------- | --------------- | ------------------------- | ------------------------------------------------------------ | | Classification, summarization, extraction, Q&A | Single LLM call | **Claude API** | One request, one response | | Batch processing or embeddings | Single LLM call | **Claude API** | Specialized endpoints | | Multi-step pipelines with code-controlled logic | Workflow | **Claude API + tool use** | You orchestrate the loop | | Custom agent with your own tools | Agent | **Claude API + tool use** | Maximum flexibility | | Server-managed stateful agent with workspace | Agent | **Managed Agents** | Anthropic runs the loop and hosts the tool-execution sandbox | | Persisted, versioned agent configs | Agent | **Managed Agents** | Agents are stored objects; sessions pin to a version | | Long-running multi-turn agent with file mounts | Agent | **Managed Agents** | Per-session containers, SSE event stream, Skills + MCP | | Agent that runs on a schedule (cron, "every night") | Agent | **Managed Agents** - scheduled deployments | Deployments fire sessions autonomously; no client-side scheduler | | Agent work that must meet a quality bar ("until it's right") | Agent | **Managed Agents** - outcomes | A separate grader iterates the agent against your rubric until it passes | > **Note:** Managed Agents is the right choice when you want Anthropic to run the agent loop *and* host the container where tools execute - file ops, bash, code execution all run in the per-session workspace. If you want to host the compute yourself or run your own custom tool runtime, Claude API + tool use is the right choice - use the tool runner for the agentic loop - its per-turn hooks still give you approval gates, logging, error interception, and conditional execution (see `shared/tool-use-concepts.md`) - or the manual loop when you want to own the entire loop yourself.