ai-agents-agent-with-tools-and-you-need-to-build-an-agent-that-can-call-external--fc9fc1fc

THEN Define a dataclass for dependencies, a Pydantic model for output, then create an Agent with deps_type and output_type. Use @agent.tool to register tool functions and RunContext to access dependencies. Optionally use @agent.instructions for dynamic instructions.

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

@dataclass
class SupportDependencies:
    customer_id: int
    db: DatabaseConn

class SupportOutput(BaseModel):
    support_advice: str = Field(description='Advice')
    block_card: bool = Field(description='Block card?')
    risk: int = Field(ge=0, le=10)

support_agent = Agent('openai:gpt-5.2', deps_type=SupportDependencies, output_type=SupportOutput, instructions='You are a support agent.')

@support_agent.instructions
async def add_customer_name(ctx: RunContext[SupportDependencies]) -> str:
    return f"Customer name is {await ctx.deps.db.customer_name(id=ctx.deps.customer_id)}"

@support_agent.tool
async def customer_balance(ctx: RunContext[SupportDependencies], include_pending: bool) -> float:
    return await ctx.deps.db.customer_balance(id=ctx.deps.customer_id, include_pending=include_pending)