# AI Skel TS Usage

> Scaffold a complete AI agent application skeleton with LLM integration, tool calling, observability, cost tracking, session management, and content fetching using @korchasa/ai-skel-ts. Use when the user asks to create an AI agent, add LLM integration, scaffold an AI application, or mentions "ai-skel", "agent skeleton", or "AI scaffold". Works with any programming language.

- Skill: `korchasa/ai-skel-ts-usage` (Agent Skill, multi-file: 5 files)
- Install (CLI): `npx skillmds@latest add korchasa/ai-skel-ts-usage`
- Raw SKILL.md: https://api.skillmd.com/api/skills/korchasa/ai-skel-ts-usage/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: AI & ML
- License: MIT
- Author: korchasa (https://skillmd.com/u/korchasa)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/korchasa/ai-skel-ts-usage

---


# AI Agent Scaffold

Generates a production-grade AI agent skeleton directly in the target project. The scaffold follows battle-tested patterns from the [ai-skel-ts](https://github.com/korchasa/ai-skel-ts) reference implementation.

## When to Use

- User asks to create a new AI agent or AI-powered application
- User asks to add LLM integration to an existing project
- User mentions "scaffold", "skeleton", "ai-skel", or "agent framework"

## Architecture Overview

The skeleton consists of 10 modules organized into 4 layers:

```
+---------------------------------------------------+
|                   Agent Layer                      |
|  Agent (stateful conversation + tool dispatch)     |
+----------------+----------------+-----------------+
|  LLM Layer     |  Tools Layer   |  Session Layer  |
|  LLM Request   |  MCP Client    |  History Compact|
|  (retry,       |  (protocol     |  (trim or       |
|   validate,    |   bridge,      |   summarize,    |
|   observe)     |   namespace)   |   tool-pair     |
|                |                |   consistency)  |
+----------------+----------------+-----------------+
|              Observability Layer                   |
|  Logger | Cost Tracker | Run Context | Debug I/O  |
+---------------------------------------------------+
|              Content Layer                         |
|  Local Fetcher | Brave Search | Jina Scraper      |
+---------------------------------------------------+
```

## Scaffold Workflow

When generating the scaffold, follow these steps:

### Step 1: Detect Project Context

1. Identify the target programming language and runtime
2. Identify the package manager and dependency management approach
3. Identify existing project structure conventions (src/, lib/, internal/, etc.)
4. Determine which LLM SDK is appropriate for the language:
   - **TypeScript/JavaScript**: Vercel AI SDK (`ai` package)
   - **Python**: `openai`, `anthropic`, `google-generativeai`, or `litellm`
   - **Go**: `github.com/sashabaranov/go-openai` or provider SDKs
   - **Rust**: `async-openai` or provider SDKs
   - **Other**: use the provider's HTTP API directly

### Step 2: Generate Modules Bottom-Up

Generate modules in this order (each depends only on previously generated ones):

1. **Logger** — zero dependencies
2. **Cost Tracker** — depends on Logger
3. **Run Context** — depends on Logger
4. **LLM Requester** — depends on Logger, Cost Tracker, Run Context
5. **Session Compactor** — depends on Logger
6. **MCP Client** — depends on Logger (optional, skip if not needed)
7. **Agent** — depends on LLM Requester, Session Compactor, MCP Client, Run Context
8. **Fetchers** — depends on Run Context (optional, add as needed)

### Step 3: Add Tests

For each module, generate at minimum:
- Unit tests with mocked dependencies
- One integration-style test with real interfaces (but mocked HTTP/LLM)

### Step 4: Wire Entry Point

Create a main entry point (mod.ts / main.py / main.go / etc.) that re-exports public API.

## Module Specifications

Each module below includes: purpose, key interfaces, algorithm, and critical implementation details. For full reference implementations in TypeScript, see the reference files.

---

### 1. Logger

**Purpose**: Structured logging with levels, context, and timestamps.

**Interface**:
- Constructor: `(context: string, logLevel: "debug"|"info"|"warn"|"error")`
- Methods: `debug(msg, meta?)`, `info(msg, meta?)`, `warn(msg, meta?)`, `error(msg, error?)`
- Factory: `createFromLevelString(context, levelString)` — validates level, warns and falls back to "debug"

**Algorithm**: Compare numeric level values (debug=0, info=1, warn=2, error=3). Log only if message level >= configured level.

**Key detail**: Error objects need special serialization (JSON.stringify(Error) returns "{}"). Extract name, message, stack explicitly.

Reference: [reference-observability.md](references/reference-observability.md)

---

### 2. Cost Tracker

**Purpose**: Accumulate LLM token usage and costs across requests.

**Interface**:
- `addCost(cost: number)` — adds USD cost, increments request counter
- `addTokens(inputTokens, outputTokens)` — accumulates token counts
- `getReport()` → `{totalCost, totalInputTokens, totalOutputTokens, totalTokens, requestCount}`
- `getFormattedReport()` → human-readable string
- `reset()` — zeroes all counters

**Pattern**: Singleton (for global tracking) OR instance (for per-run tracking). Provide both options.

Reference: [reference-observability.md](references/reference-observability.md)

---

### 3. Run Context

**Purpose**: Immutable execution context with unique run ID and debug artifact management.

**Interface**:
- `RunContext { runId, debugDir, logger, startTime, saveDebugFile() }`
- Factory: `createRunContext(logger, debugDir, runId?)` — auto-generates reverse-sortable ID if not provided
- `getSubDebugDir(ctx, stageDir)` — returns subdirectory path for a stage
- `safeSanitize(obj)` — recursively handles Error, Buffer, circular refs for serialization

**Critical algorithm** — Reverse-sortable Run ID:
```
maxMs = Date.UTC(9999, 11, 31, 23, 59, 59, 999)
reversedMs = maxMs - Date.now()
runId = toISO(reversedMs) + microSequence
```
This makes newest runs sort first in file listings.

Reference: [reference-core.md](references/reference-core.md)

---

### 4. LLM Requester

**Purpose**: Provider-agnostic LLM interface with retry, validation, self-correction, and observability.

**This is the most complex module.** Read [reference-core.md](references/reference-core.md) carefully.

**Interface**:
- `ModelURI` — parses `protocol://provider/model?params` (e.g., `chat://openai/gpt-4o?timeout=60000`)
- `createLlmRequester(modelUri, logger, costTracker, ctx)` → requester function
- Requester function: `(messages, identifier, schema?, tools?, maxSteps?, stageName, settings?) → GenerateResult`
- `GenerateResult { result, text, toolCalls, toolResults, newMessages, steps, estimatedCost, inputTokens, outputTokens, validationError?, rawResponse? }`

**Core algorithm** (retry loop with self-correction):
```
parse URI → create provider instance → return requester function

requester(messages, schema, tools, ...):
  write initial YAML log file
  for attempt = 1..MAX_RETRIES(3):
    set timeout via AbortController
    call LLM SDK (generateText / chat completion)

    on success:
      track cost/tokens
      aggregate newMessages from steps
      update YAML log
      return result

    on validation error (schema mismatch):
      append assistant message (raw response)
      append user message (error description)  <- SELF-CORRECTION
      update YAML log
      retry

    on fatal API error (401/403/400):
      return error immediately (no retry)

    on transient error:
      exponential backoff: delay = 1000ms * 2^(attempt-1) + jitter(20%)
      retry
```

**Key details**:
- API key resolution: URI param > environment variable (`{PROVIDER}_API_KEY`)
- AbortController.abort() must be wrapped in try-catch (listeners can throw)
- Mask apiKey in URI toString() for logging
- Settings from URI are defaults; per-request settings override them

Reference: [reference-core.md](references/reference-core.md)

---

### 5. Session Compactor

**Purpose**: Manage conversation context window by trimming or summarizing history.

**Interface**:
- `HistoryCompactor { compact(messages) → messages, estimateSymbols(message) → number }`
- `SimpleHistoryCompactor(maxSymbols)` — trims oldest messages
- `SummarizingHistoryCompactor(maxSymbols, summaryTokenThreshold, summaryGenerator)` — LLM-powered

**Algorithm** (SimpleHistoryCompactor):
```
trimBySymbolLimit:
  iterate messages from newest to oldest
  accumulate symbol weight (JSON.stringify length)
  stop when budget exceeded

ensureToolConsistency:
  collect all tool-call IDs and tool-result IDs
  remove messages with orphaned tool-calls (no matching result)
  remove messages with orphaned tool-results (no matching call)
```

**Algorithm** (SummarizingHistoryCompactor):
```
estimate token count (symbols / 4)
if under threshold → delegate to SimpleHistoryCompactor
if over threshold:
  split: messages[0..splitPoint] → summarize, messages[splitPoint..] → keep
  splitPoint = index before last assistant message
  call SummaryGenerator.generateSummary(toSummarize) → summary message
  ensure proper message alternation (add dummy user message if needed)
  apply tool consistency check
on error → fallback to SimpleHistoryCompactor
```

Reference: [reference-session.md](references/reference-session.md)

---

### 6. MCP Client (optional)

**Purpose**: Bridge between Model Context Protocol servers and the LLM tool interface.

**Interface**:
- `McpClientWrapper(config, logger, name)` — config is either `{type:"stdio", command, args}` or `{type:"sse", url}`
- `connect()` / `disconnect()` — lifecycle management
- `getTools()` → `Record<string, Tool>` — discovers and converts tools

**Key details**:
- Tool namespacing: prefix tool names with server name (`serverName__toolName`) to prevent collisions
- Tool conversion: MCP JSON Schema → LLM SDK Tool format (use `jsonSchema()` helper if available)
- Execute: call MCP `tools/call`, extract text content from response parts

Reference: [reference-session.md](references/reference-session.md)

---

### 7. Agent

**Purpose**: Stateful conversation runner with tool integration and history management.

**Interface**:
- `Agent(llm, mcpClients?, ctx, systemPrompt?, compactor?, tools?)`
- `init()` — connects MCP clients, aggregates all tools
- `run(input)` → `GenerateResult` — full access to results
- `chat(input)` → `string` — convenience wrapper
- `getHistory()` → messages array

**Algorithm**:
```
constructor:
  store params
  if systemPrompt: push system message to history

init:
  for each mcpClient:
    connect()
    getTools() → merge into this.tools

run(input):
  push user message to history
  if compactor: compact history
  call llm(messages, tools, maxSteps=10, ...)
  if error: throw
  append all newMessages to history
  return result

chat(input):
  return run(input).text
```

Reference: [reference-core.md](references/reference-core.md)

---

### 8-10. Fetchers (optional)

Three content acquisition strategies. Add only what the project needs.

**Local Fetcher**: HTML → clean text + metadata via Readability algorithm
**Brave Search**: REST API client with 429 retry and rate-limited batch search
**Jina Scraper**: Dual-endpoint (search + reader) API client with rich options

Reference: [reference-fetchers.md](references/reference-fetchers.md)

---

## Language Adaptation Guidelines

When adapting patterns to a target language:

| Concept | TypeScript | Python | Go | Rust |
|---------|-----------|--------|-----|------|
| Interfaces | `interface` / `type` | `Protocol` / `ABC` | `interface` | `trait` |
| Generics | `<T>` | `Generic[T]` | `[T any]` | `<T>` |
| Async | `async/await` | `async/await` | goroutines/channels | `async/await` |
| Error handling | try/catch + types | try/except + types | error return | Result<T, E> |
| Dependency injection | constructor params | constructor / `__init__` | struct fields | struct fields |
| Singleton | static instance | module-level / `__new__` | `sync.Once` | `once_cell::Lazy` |
| Schema validation | Zod | Pydantic | struct tags + validator | serde + validator |
| URI parsing | `URL` class | `urllib.parse` | `net/url` | `url` crate |

## File Organization

Adapt to the project's conventions. Suggested structure:

```
{src_dir}/
+-- agent/
|   +-- agent.{ext}
|   +-- agent_test.{ext}
+-- llm/
|   +-- requester.{ext}
|   +-- model_uri.{ext}
|   +-- requester_test.{ext}
+-- run_context/
|   +-- context.{ext}
|   +-- context_test.{ext}
+-- cost_tracker/
|   +-- tracker.{ext}
|   +-- tracker_test.{ext}
+-- logger/
|   +-- logger.{ext}
|   +-- logger_test.{ext}
+-- session/
|   +-- compactor.{ext}
|   +-- summary_generator.{ext}
|   +-- compactor_test.{ext}
+-- mcp/                          # optional
|   +-- client.{ext}
+-- fetchers/                     # optional
|   +-- local/
|   +-- brave/
|   +-- jina/
+-- mod.{ext}                     # public API entry point
```

## Critical Rules

1. **No stubs**: Every function must have a real implementation
2. **Observability first**: Every LLM call writes a YAML debug artifact to debugDir
3. **Self-correction**: On schema validation failure, feed the error back to the LLM
4. **Tool-pair consistency**: Never leave orphaned tool-calls or tool-results in history
5. **Reverse-sortable IDs**: Run IDs sort newest-first in file listings
6. **Mask secrets**: API keys must never appear in logs or debug files
7. **Exponential backoff**: `delay = baseDelay * 2^(attempt-1) + jitter`
8. **Safe serialization**: Handle Error objects, Buffers, circular references before serializing
9. **URI-based config**: Model configuration via `protocol://provider/model?params`
10. **Graceful degradation**: Summarization fails → fall back to trimming; MCP fails → continue without tools

## Checklist

After generating the scaffold, verify:

- [ ] All modules compile/lint without errors
- [ ] Tests pass
- [ ] LLM Requester has retry loop with self-correction
- [ ] Agent preserves all intermediate tool-call messages in history
- [ ] Session Compactor maintains tool-call/tool-result pair consistency
- [ ] Run Context generates reverse-sortable IDs
- [ ] Logger handles Error serialization
- [ ] Cost Tracker accumulates across requests
- [ ] Debug artifacts written as YAML to structured directories
- [ ] API keys masked in all log output