Building LLM-Powered Applications with Claude Agent Skill

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;…

Context cost
464.6k tokensestimated from the bundle; more than a 200k window holds
Bundle
96 files · 2079.3 kB4 scripts among them — read before you run
Licence
Complete terms in LICENSE.txtthe author’s own terms
Last change
—no release on file
Servers it uses
Noneruns standalone

What it does

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 from memory; OR the task is LLM-shaped with provider unstated…

What this skill changes about the agent has not been set out here as a list. Its SKILL.md, shown below, says it in the author’s own words.

The skill itself

A skill is instructions the model reads, so you can see what you are getting: below is the start of its SKILL.md. The front matter loads with every session, the body loads when the skill triggers, and the whole file comes with the install.

SKILL.md105.1 kB · preview
--- name: claude-api license: Complete terms in LICENSE.txt ---
10# Building LLM-Powered Applications with Claude
11
12This 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.
13
14## Before You Start
15
16Scan 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.)
17
18## Output Requirement
19
20When the user asks you to add, modify, or implement a Claude feature, your code must call Claude through one of:
21
221. **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.
232. **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.
24
25Never 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.
26
27**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.
28
This is a preview of SKILL.md. Download or install the skill to get the whole thing.
In the file
SKILL.md14,600 words
Files96
LicenceComplete terms in LICENSE.txt
Why you can read it

Nothing in a skill executes. The client loads the text and the model follows it, so a skill can be audited the way a runbook is — by reading it.

What it costs in context

Skills are not billed by the call. They are paid for in context: every token the instructions occupy is a token your code, your diff and your conversation cannot use. Here is what this one takes and when it takes it.

≈290
always loaded
The name and description, so the model knows the skill exists and when to reach for it.
464,285
on trigger
The instruction body and 95 supporting files, read only when the skill fires.
2.3×
a 200k window
It does not fit in the window: loaded whole, it would need more room than the model has.
050k100k150k200k context window

464.6k tokens, estimated from the bundle at four bytes to the token — more than the whole window, so it cannot all be held at once: the model reads SKILL.md when the skill fires and the other files only as the instructions call for them. Heavy. Teams tend to install this one per project rather than globally, and load it only when the job comes up.

Servers bill, skills cost

A server charges by the month. A skill charges once per session, in context, and then keeps charging it for as long as the session lives.

Before and after

The same question, put to the same model twice: once as it comes, and once with these instructions loaded.

No worked example has been published for this skill yet.

The procedure it runs

The procedure has not been set out here step by step. It is in the body of its SKILL.md: the start of it is shown above, and the whole file comes with the install.

Prose, not code

These steps are written for a model to follow, not executed by a runtime. It can still be told to skip one, and it will say so when it does.

Servers it uses

None. This skill calls no MCP servers at all.

Everything it needs is in the instructions, so it works in a project with nothing connected — the model reads the file and changes how it works with what it can already reach.

Its SKILL.md does not declare which tools it asks the agent for, so what it touches is whatever the instructions themselves ask for — read them before you install it.

What it asks for
Writes filesnot declared
Network accessnot declared

This SKILL.md carries no allowed-tools line, so neither is declared. A skill grants no permissions of its own — it can only ask for tools your client already has.

What it will not do

Every skill is narrow, and the useful ones say where they stop. These are the jobs this one is the wrong tool for.

What this skill is not for has not been published here. Nothing is implied by that: it is a section the author has not filled in.

What is in the bundle

96 files, 2079.3 kB on disk. Mostly text — the instructions the model reads — with 4 scripts in it that your client would run only if the instructions tell it to.

  • SKILL.md105.1 kB
  • LICENSE.txt11.3 kB
  • curl/examples.md9.7 kB
  • curl/managed-agents.md10.8 kB
  • shared/admin-api.md11.6 kB
  • shared/agent-design.md8.7 kB
  • shared/anthropic-cli.md24.0 kB
  • shared/claude-platform-on-aws.md4.4 kB
  • shared/cost-optimization.md58.4 kB
  • shared/error-codes.md20.8 kB
  • shared/live-sources.md17.7 kB
  • shared/managed-agents-api-reference.md35.3 kB
  • shared/managed-agents-client-patterns.md12.1 kB
  • shared/managed-agents-core.md33.5 kB
  • shared/managed-agents-environments.md14.2 kB
  • shared/managed-agents-events.md26.0 kB
  • shared/managed-agents-memory.md11.4 kB
  • shared/managed-agents-multiagent.md66.6 kB
  • shared/managed-agents-onboarding-from-quickstart.md19.8 kB
  • shared/managed-agents-onboarding-from-url.md32.7 kB
  • shared/managed-agents-onboarding.md16.8 kB
  • shared/managed-agents-outcomes.md9.0 kB
  • shared/managed-agents-overview.md14.6 kB
  • shared/managed-agents-scheduled-deployments.md9.6 kB
  • shared/managed-agents-self-hosted-sandboxes.md27.9 kB
  • shared/managed-agents-tools.md37.9 kB
  • shared/managed-agents-webhooks.md11.3 kB
  • shared/model-migration.md346.3 kB
  • shared/models.md17.5 kB
  • shared/platform-availability.md7.4 kB
  • shared/preserved-thinking-migration.md64.0 kB
  • shared/prompt-audit.md49.3 kB
  • shared/prompt-caching.md33.1 kB
  • shared/token-counting.md1.6 kB
  • shared/tool-use-concepts.md44.4 kB
  • csharp/claude-api/README.md18.9 kB
  • csharp/claude-api/batches.md0.4 kB
  • csharp/claude-api/files-api.md0.9 kB
  • csharp/claude-api/streaming.md0.8 kB
  • csharp/claude-api/tool-use.md7.6 kB
  • go/claude-api/README.md8.5 kB
  • go/claude-api/files-api.md0.9 kB
  • go/claude-api/streaming.md1.0 kB
  • go/claude-api/tool-use.md10.0 kB
  • go/managed-agents/README.md22.5 kB
  • java/claude-api/README.md11.9 kB
  • java/claude-api/files-api.md1.2 kB
  • java/claude-api/streaming.md0.7 kB
  • java/claude-api/tool-use.md11.1 kB
  • java/managed-agents/README.md20.5 kB
  • php/claude-api/README.md6.6 kB
  • php/claude-api/batches.md0.4 kB
  • php/claude-api/files-api.md0.5 kB
  • php/claude-api/streaming.md0.7 kB
  • php/claude-api/tool-use.md9.7 kB
  • php/managed-agents/README.md16.6 kB
  • python/claude-api/README.md20.6 kB
  • python/claude-api/batches.md5.7 kB
  • python/claude-api/files-api.md4.5 kB
  • python/claude-api/sdk-upgrade.md28.8 kB
  • python/claude-api/streaming.md11.9 kB
  • python/claude-api/tool-use.md21.4 kB
  • python/managed-agents/README.md14.8 kB
  • ruby/claude-api/README.md4.8 kB
  • ruby/claude-api/streaming.md0.2 kB
  • ruby/claude-api/tool-use.md2.7 kB
  • ruby/managed-agents/README.md12.2 kB
  • shared/evals/build-eval.md54.8 kB
  • shared/evals/cost-hillclimb.md31.7 kB
  • shared/evals/eval-audit.md27.9 kB
  • shared/evals/eval-hillclimb.md69.2 kB
  • shared/managed-agents-quickstarts/bug-hunter.md8.1 kB
  • shared/managed-agents-quickstarts/contract-tracker.md1.8 kB
  • shared/managed-agents-quickstarts/data-analyst.md1.6 kB
  • shared/managed-agents-quickstarts/deep-researcher.md2.4 kB
  • shared/managed-agents-quickstarts/explainer-video-maker.md4.9 kB
  • shared/managed-agents-quickstarts/field-monitor.md2.1 kB
  • shared/managed-agents-quickstarts/incident-commander.md1.7 kB
  • shared/managed-agents-quickstarts/performance-tuner.md11.4 kB
  • shared/managed-agents-quickstarts/sprint-retro-facilitator.md2.1 kB
  • shared/managed-agents-quickstarts/structured-extractor.md1.5 kB
  • shared/managed-agents-quickstarts/support-agent.md1.5 kB
  • shared/managed-agents-quickstarts/support-to-eng-escalator.md1.8 kB
  • shared/managed-agents-quickstarts/watchlist-scanner.md5.6 kB
  • shared/preserved-thinking-migration/causes.md39.7 kB
  • shared/preserved-thinking-migration/drop_block_probe.py66.6 kB
  • shared/preserved-thinking-migration/prefix_diff.py94.0 kB
  • typescript/claude-api/README.md15.8 kB
  • typescript/claude-api/batches.md2.6 kB
  • typescript/claude-api/files-api.md2.4 kB
  • typescript/claude-api/streaming.md9.5 kB
  • typescript/claude-api/tool-use.md24.3 kB
  • typescript/managed-agents/README.md14.0 kB
  • shared/evals/report/SCHEMA.md16.1 kB
  • shared/evals/report/build-report-lite.mjs27.3 kB
  • shared/evals/report/runner-scaffold.mjs33.1 kB
What is not in it

A skill installs nothing and depends on nothing: it is a folder your client reads. This one carries 4 scripts beside the text, so the bundle is 96 files you can review in full before installing. The licence the author declares covers the templates and examples as well as the instructions.

Install

Installing copies the bundle into your project. Nothing runs at install time — the files sit on disk until the model reads them.

# Building LLM-Powered Applications with Claude · 464.6k tokens when loaded · macOS, Linux mkdir -p .claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/building-llm-powered-applications-with-claude/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/building-llm-powered-applications-with-claude" ] && { [ ! -e .claude/skills/building-llm-powered-applications-with-claude ] || { mv .claude/skills/building-llm-powered-applications-with-claude "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/building-llm-powered-applications-with-claude" .claude/skills/ && echo "Installed .claude/skills/building-llm-powered-applications-with-claude"
On Windows, or any OS with Node 20+
npx mcprush@latest skill add anthropics/building-llm-powered-applications-with-claude

Windows PowerShell says 'running scripts is disabled on this system'? Run Set-ExecutionPolicy -Scope CurrentUser RemoteSigned once, or type npx.cmd instead of npx (codex.cmd, gemini.cmd, grok.cmd likewise). PowerShell 7 needs neither. Writes to .claude/skills/building-llm-powered-applications-with-claude/ in the current project. For every project instead, run mkdir -p ~/.claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/building-llm-powered-applications-with-claude/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/building-llm-powered-applications-with-claude" ] && { [ ! -e ~/.claude/skills/building-llm-powered-applications-with-claude ] || { mv ~/.claude/skills/building-llm-powered-applications-with-claude "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/building-llm-powered-applications-with-claude" ~/.claude/skills/ && echo "Installed ~/.claude/skills/building-llm-powered-applications-with-claude" (macOS, Linux) — or add --global to the npx line. The curl line replaces .claude/skills/building-llm-powered-applications-with-claude/ only after the download succeeds, so files left there by another skill of the same name, or by an older release, do not mix in. A copy already there is moved aside, not deleted, and the line prints where. It appears as claude-api in Gemini CLI, Codex, Copilot and Grok (its own name); Claude Code lists it by the folder name, building-llm-powered-applications-with-claude.

Which clients pick it up on their own

A skill is a folder of text. Most of these read a skills folder and pick it up without being told; the rest take the same folder another way — an upload in the app, a parameter on an API call — and then choose it by its description just the same.

Claude Code.claude/skills/
Claude DesktopCustomize › Skills
ChatGPTSkills › Create › Upload
Cursor.cursor/skills/
VS Code.github/skills/
Codex CLI.agents/skills/
Gemini CLI.gemini/skills/
Grok Build.grok/skills/
Microsoft CopilotSkills › Upload a skill
PerplexityComputer › Skills › Upload a skill
DeepSeek Harness.dsh/skills/
Zed.agents/skills/
Devin Desktop.devin/skills/
Windsurf (legacy).windsurf/skills/
OpenAI Agents SDKInstructions or sandbox Skills
HTTP / APIa request parameter
This release
Versionnot versioned
Publishedno release date on file
PriceFree
Referenceanthropics/building-llm-powered-applications-with-claude

Versions

Its author publishes no version number, so there is nothing here to pin to: what you install is the folder as it stands today. Instructions change more often than APIs do — a skill can be rewritten entirely without anything it depends on moving.

Pinning

Nothing to pin to: this skill carries no version number of its own. What you install is what the folder holds on the day you install it.

Reviews

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Anybody with an account, one review each. It carries the version that was current when you wrote it, and the publisher may reply once.

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