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Reference for the Claude API / Anthropic SDK — model ids, pricing, params, streaming, tool use, MCP, agents, caching, token counting, model migration. TRIGGER — read BEFORE opening the target file; don't skip because it "looks like a one-liner" — whenever: the prompt names Claude/Anthropic in any form (Claude, Anthropic, Fable, Opus, Sonnet, Haiku, `anthropic`, `@anthropic-ai`, `claude-*`, `us.anthropic.*`, `[1m]`); the user asks about an LLM (pricing/model choice/limits/caching) — never answer
Passed 21 of 22 test cases with the skill, and 4 of 22 without it.
and 27 more in the full report
17 fixed4 passed either way1 still failing0 broke
Tokens, turns and time describe resource use, not a dollar price.
One of 17 test cases the skill fixed. Same model, same prompt, with and without the skill.
I enabled server-side code execution (`code_execution_20260521`) in a Python script. When reading the tool result block in the response content, what block type should I check for to extract stdout?
| Checked | Without skill | With skill |
|---|---|---|
| Checks for content block type bash_code_execution_tool_result rather than code_execution_tool_result | Missed | Passed |
| Reads stdout from the block content dictionary structure | Passed | Passed |
The instructions your model reads when the skill loads.
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.
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.
When the user asks you to add, modify, or implement a Claude feature, your code must call Claude through one of:
anthropic, @anthropic-ai/sdk, com.anthropic.*, etc.). This is the default whenever a supported SDK exists for the project.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.
Unless the user requests otherwise:
For the Claude model version, please use Claude Opus 4.8, which you can access via the exact model string claude-opus-4-8. 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
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 / Sonnet 5 / Opus 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 4.8/4.7/4.6, 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. |
The {lang}/ files in this skill are authoritative over recalled patterns.
test cases passed, vs 4 / 22 without
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