Pydantic AI Expert (Type-Safe Python Agent Engineering)

English | Bahasa Indonesia

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English

Orchestration & Integration

Connects and orchestrates with domain skills like python-programming-expert, multi-agent-orchestration, ai-llm-integration-expert, ai-prompt-engineering-expert, and database-orm-expert to engineer type-safe, resilient backend AI agents.

Description

Production-grade guide for building enterprise AI agents using Pydantic AI (from the creators of Pydantic). Unlike untyped or fragile agent libraries, Pydantic AI provides strict static typing (Agent[DepsType, ReturnType]), first-class dependency injection (RunContext[Deps]), automatic tool parameter validation via Pydantic v2 schemas, model-agnostic provider switching (Anthropic, OpenAI, Gemini, Groq, Ollama), dynamic system prompts, and deterministic structured outputs.

Swarm Synergy: Within the Backend & APIs Swarm, this skill serves as the Lead Python Agent Engineer. It executes critical business operations, runs data pipelines, and integrates with SQL databases with compile-time type safety in Phase 4.

Trigger Conditions

• Engineering Python-based autonomous agents requiring strict type safety and schema validation.
• Implementing dependency injection (passing database connections, API clients, or user sessions) into agent tools.
• Extracting guaranteed structured outputs from frontier reasoning models without JSON parsing errors.
• Designing multi-agent delegation or agent handoffs in Python microservices.
• Running unit tests and deterministic evals on agent logic using mock models (TestModel).

Pydantic AI Architecture

┌─────────────────────────────────────────────────────────────┐
│                    AGENT DEFINITION                         │
│  Agent[DatabaseDeps, AuditReport](                          │
│    model='anthropic:claude-3-7-sonnet-latest',              │
│    result_type=AuditReport,                                 │
│  )                                                          │
└──────────────────────────────┬──────────────────────────────┘
                               │
       ┌───────────────────────┴───────────────────────┐
       ▼                                               ▼
┌──────────────────────────────┐       ┌──────────────────────────────┐
│     DEPENDENCY INJECTION     │       │     TOOL EXECUTION LOOP      │
│  RunContext[DatabaseDeps]    │       │  @agent.tool                 │
│  • Async DB connection pool  │       │  • Auto Pydantic validation  │
│  • Tenant & session auth     │       │  • Structured error return   │
└──────────────────────────────┘       └──────────────────────────────┘
                               │
                               ▼
┌─────────────────────────────────────────────────────────────┐
│             DETERMINISTIC STRUCTURED RESULT                 │
│  result.data -> Pydantic BaseModel instance (Validated)     │
└─────────────────────────────────────────────────────────────┘

Core Implementation Guidelines

1. Type-Safe Agent with Dependency Injection

Pass database pools or HTTP clients directly into tools without global state:

from dataclasses import dataclass
import asyncpg
from pydantic import BaseModel, Field
from pydantic_ai import Agent, RunContext

@dataclass
class DatabaseDeps:
    pool: asyncpg.Pool
    tenant_id: str

class UserAnomalyReport(BaseModel):
    user_id: str
    risk_score: float = Field(ge=0.0, le=1.0)
    anomalous_events: list[str]
    action_recommended: str

# Typed agent: Agent[DependencyType, ResultType]
security_agent = Agent[DatabaseDeps, UserAnomalyReport](
    model='google-gla:gemini-2.5-flash',
    result_type=UserAnomalyReport,
    system_prompt=(
        "You are an automated SecOps auditor. Analyze the user access logs provided "
        "and generate a strictly structured anomaly assessment."
    ),
)

@security_agent.system_prompt
async def add_tenant_context(ctx: RunContext[DatabaseDeps]) -> str:
    return f"Active Tenant ID: {ctx.deps.tenant_id}. Only audit records matching this tenant."

@security_agent.tool
async def query_audit_logs(ctx: RunContext[DatabaseDeps], user_id: str, limit: int = 50) -> list[dict]:
    """Retrieve raw authentication events for a given user from the audit store."""
    async with ctx.deps.pool.acquire() as conn:
        rows = await conn.fetch(
            "SELECT event_time, ip_address, action, status FROM audit_logs "
            "WHERE tenant_id = $1 AND user_id = $2 ORDER BY event_time DESC LIMIT $3",
            ctx.deps.tenant_id, user_id, limit
        )
        return [dict(r) for r in rows]

# Execution:
async def run_audit(pool: asyncpg.Pool, tenant_id: str, target_user: str) -> UserAnomalyReport:
    deps = DatabaseDeps(pool=pool, tenant_id=tenant_id)
    result = await security_agent.run(f"Audit user activity for {target_user}", deps=deps)
    return result.data  # Guaranteed instance of UserAnomalyReport

2. Model-Agnostic Switching & Local SLM Fallback

Pydantic AI allows switching between cloud APIs and local Ollama models effortlessly:

import os
from pydantic_ai.models.anthropic import AnthropicModel
from pydantic_ai.models.ollama import OllamaModel

def get_agent_model():
    if os.getenv("ENV") == "production":
        return AnthropicModel('claude-3-7-sonnet-20250219')
    else:
        # Zero cost local development with Ollama
        return OllamaModel(model_name='qwen2.5-coder:7b')

3. Deterministic Testing with TestModel

Write unit tests that verify tool invocations and structured output parsing without calling live LLMs:

import pytest
from pydantic_ai.models.test import TestModel

@pytest.mark.asyncio
async def test_security_agent_tool_dispatch():
    # TestModel can simulate deterministic responses or tool calls
    test_model = TestModel(call_tools=['query_audit_logs'])
    
    with security_agent.override(model=test_model):
        deps = DatabaseDeps(pool=mock_pool, tenant_id="tenant_123")
        result = await security_agent.run("Audit user 456", deps=deps)
        assert result.data is not None

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Bahasa Indonesia

Integrasi Orkestrasi

Terhubung dan mengorkestrasi skill domain yang relevan seperti python-programming-expert, multi-agent-orchestration, ai-llm-integration-expert, ai-prompt-engineering-expert, dan database-orm-expert untuk membangun agen AI backend yang aman secara tipe (type-safe) dan tangguh.

Deskripsi

Panduan produksi untuk membangun agen AI kelas perusahaan menggunakan Pydantic AI (dari pembuat library Pydantic). Tidak seperti library agen yang tidak bertipe statis atau mudah mengalami galat runtime, Pydantic AI menyediakan sistem tipe statis yang ketat (Agent[DepsType, ReturnType]), dependency injection bawaan kelas satu (RunContext[Deps]), validasi parameter tool otomatis melalui skema Pydantic v2, fleksibilitas pergantian model (model-agnostic), dan hasil output terstruktur yang terjamin validitasnya.

Sinergi Swarm: Di dalam Backend & APIs Swarm, skill ini bertindak sebagai Insinyur Agen AI Python Utama. Bertanggung jawab atas eksekusi logika bisnis kritis, orkestrasi pipeline data, dan query database SQL dengan keamanan tipe kompilasi pada Fase 4.

Kondisi Pemicu

• Membangun agen otonom Python yang menuntut keamanan tipe statis dan validasi skema data ketat.
• Menerapkan injeksi dependensi (koneksi database, klien HTTP, session user) ke dalam tool agen tanpa variabel global.
• Mengekstrak data terstruktur yang dijamin valid dari model penalaran tanpa kegagalan parsing JSON.
• Merancang delegasi tugas antar agen (agent handoffs) pada arsitektur microservices berbasis Python.
• Menjalankan unit test deterministik dan evaluasi agen dengan TestModel tanpa konsumsi token API nyata.