PydanticAI — Typed AI Agents in Python

Overview

This public intake copy packages

plugins/antigravity-awesome-skills-claude/skills/pydantic-ai

https://github.com/sickn33/antigravity-awesome-skills

Use it when the operator needs the upstream workflow, support files, and repository context to stay intact while the public validator and private enhancer continue their normal downstream flow.

This intake keeps the copied upstream files intact and uses

metadata.json

ORIGIN.md

PydanticAI — Typed AI Agents in Python

Imported source sections that did not map cleanly to the public headings are still preserved below or in the support files. Notable imported sections: How It Works, Security & Safety Notes, Common Pitfalls, Limitations.

When to Use This Skill

Use this section as the trigger filter. It should make the activation boundary explicit before the operator loads files, runs commands, or opens a pull request.

• Use when building Python AI agents that call tools and return structured data
• Use when you need validated, typed LLM outputs (not raw strings)
• Use when you want to write unit tests for agent logic without hitting a real LLM
• Use when switching between LLM providers without rewriting agent code
• Use when the user asks about Agent, @agent.tool, RunContext, ModelRetry, or result_type
• Use when the request clearly matches the imported source intent: Build production-ready AI agents with PydanticAI — type-safe tool use, structured outputs, dependency injection, and multi-model support.

Operating Table

metadata.json

ORIGIN.md

SKILL.md

SKILL.md

## Related Skills

Workflow

This workflow is intentionally editorial and operational at the same time. It keeps the imported source useful to the operator while still satisfying the public intake standards that feed the downstream enhancer flow.

1. Confirm the user goal, the scope of the imported workflow, and whether this skill is still the right router for the task.
2. Read the overview and provenance files before loading any copied upstream support files.
3. Load only the references, examples, prompts, or scripts that materially change the outcome for the current request.
4. Execute the upstream workflow while keeping provenance and source boundaries explicit in the working notes.
5. Validate the result against the upstream expectations and the evidence you can point to in the copied files.
6. Escalate or hand off to a related skill when the work moves out of this imported workflow's center of gravity.
7. Before merge or closure, record what was used, what changed, and what the reviewer still needs to verify.

Imported Workflow Notes

Imported: Overview

PydanticAI is a Python agent framework from the Pydantic team that brings the same type-safety and validation guarantees as Pydantic to LLM-based applications. It supports structured outputs (validated with Pydantic models), dependency injection for testability, streamed responses, multi-turn conversations, and tool use — across OpenAI, Anthropic, Google Gemini, Groq, Mistral, and Ollama. Use this skill when building production AI agents, chatbots, or LLM pipelines where correctness and testability matter.

Imported: How It Works

Step 1: Installation

pip install pydantic-ai

# Install extras for specific providers
pip install 'pydantic-ai[openai]'       # OpenAI / Azure OpenAI
pip install 'pydantic-ai[anthropic]'    # Anthropic Claude
pip install 'pydantic-ai[gemini]'       # Google Gemini
pip install 'pydantic-ai[groq]'         # Groq
pip install 'pydantic-ai[vertexai]'     # Google Vertex AI

Step 2: A Minimal Agent

from pydantic_ai import Agent

# Simple agent — returns a plain string
agent = Agent(
    'anthropic:claude-sonnet-4-6',
    system_prompt='You are a helpful assistant. Be concise.',
)

result = agent.run_sync('What is the capital of Japan?')
print(result.data)  # "Tokyo"
print(result.usage())  # Usage(requests=1, request_tokens=..., response_tokens=...)

Step 3: Structured Output with Pydantic Models

from pydantic import BaseModel
from pydantic_ai import Agent

class MovieReview(BaseModel):
    title: str
    year: int
    rating: float  # 0.0 to 10.0
    summary: str
    recommended: bool

agent = Agent(
    'openai:gpt-4o',
    result_type=MovieReview,
    system_prompt='You are a film critic. Return structured reviews.',
)

result = agent.run_sync('Review Inception (2010)')
review = result.data  # Fully typed MovieReview instance
print(f"{review.title} ({review.year}): {review.rating}/10")
print(f"Recommended: {review.recommended}")

Step 4: Tool Use

Register tools with

@agent.tool

from pydantic_ai import Agent, RunContext
from pydantic import BaseModel
import httpx

class WeatherReport(BaseModel):
    city: str
    temperature_c: float
    condition: str

weather_agent = Agent(
    'anthropic:claude-sonnet-4-6',
    result_type=WeatherReport,
    system_prompt='Get current weather for the requested city.',
)

@weather_agent.tool
async def get_temperature(ctx: RunContext, city: str) -> dict:
    """Fetch the current temperature for a city from the weather API."""
    async with httpx.AsyncClient() as client:
        r = await client.get(f'https://wttr.in/{city}?format=j1')
        data = r.json()
        return {
            'temp_c': float(data['current_condition'][0]['temp_C']),
            'description': data['current_condition'][0]['weatherDesc'][0]['value'],
        }

import asyncio
result = asyncio.run(weather_agent.run('What is the weather in Tokyo?'))
print(result.data)

Step 5: Dependency Injection

Inject services (database, HTTP clients, config) into agents for testability:

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

@dataclass
class Deps:
    db: Database
    user_id: str

class SupportResponse(BaseModel):
    message: str
    escalate: bool

support_agent = Agent(
    'openai:gpt-4o-mini',
    deps_type=Deps,
    result_type=SupportResponse,
    system_prompt='You are a support agent. Use the tools to help customers.',
)

@support_agent.tool
async def get_order_history(ctx: RunContext[Deps]) -> list[dict]:
    """Fetch recent orders for the current user."""
    return await ctx.deps.db.get_orders(ctx.deps.user_id, limit=5)

@support_agent.tool
async def create_refund(ctx: RunContext[Deps], order_id: str, reason: str) -> dict:
    """Initiate a refund for a specific order."""
    return await ctx.deps.db.create_refund(order_id, reason, ctx.deps.user_id)

# Usage
async def handle_support(user_id: str, message: str):
    deps = Deps(db=get_db(), user_id=user_id)
    result = await support_agent.run(message, deps=deps)
    return result.data

Step 6: Testing with TestModel

Write unit tests without real LLM calls:

from pydantic_ai.models.test import TestModel

def test_support_agent_escalates():
    with support_agent.override(model=TestModel()):
        # TestModel returns a minimal valid response matching result_type
        result = support_agent.run_sync(
            'I want to cancel my account',
            deps=Deps(db=FakeDb(), user_id='user-123'),
        )
    # Test the structure, not the LLM's exact words
    assert isinstance(result.data, SupportResponse)
    assert isinstance(result.data.escalate, bool)

FunctionModel for deterministic test responses:

from pydantic_ai.models.function import FunctionModel, ModelContext

def my_model(messages, info):
    return ModelResponse(parts=[TextPart('Always this response')])

with agent.override(model=FunctionModel(my_model)):
    result = agent.run_sync('anything')

Step 7: Streaming Responses

import asyncio
from pydantic_ai import Agent

agent = Agent('anthropic:claude-sonnet-4-6')

async def stream_response():
    async with agent.run_stream('Write a haiku about Python') as result:
        async for chunk in result.stream_text():
            print(chunk, end='', flush=True)
    print()  # newline
    print(f"Total tokens: {result.usage()}")

asyncio.run(stream_response())

Step 8: Multi-Turn Conversations

from pydantic_ai import Agent
from pydantic_ai.messages import ModelMessagesTypeAdapter

agent = Agent('openai:gpt-4o', system_prompt='You are a helpful assistant.')

# First turn
result1 = agent.run_sync('My name is Alice.')
history = result1.all_messages()

# Second turn — passes conversation history
result2 = agent.run_sync('What is my name?', message_history=history)
print(result2.data)  # "Your name is Alice."

Examples

Example 1: Ask for the upstream workflow directly

Use @pydantic-ai to handle <task>. Start from the copied upstream workflow, load only the files that change the outcome, and keep provenance visible in the answer.

Explanation: This is the safest starting point when the operator needs the imported workflow, but not the entire repository.

Example 2: Ask for a provenance-grounded review

Review @pydantic-ai against metadata.json and ORIGIN.md, then explain which copied upstream files you would load first and why.

Explanation: Use this before review or troubleshooting when you need a precise, auditable explanation of origin and file selection.

Example 3: Narrow the copied support files before execution

Use @pydantic-ai for <task>. Load only the copied references, examples, or scripts that change the outcome, and name the files explicitly before proceeding.

Explanation: This keeps the skill aligned with progressive disclosure instead of loading the whole copied package by default.

Example 4: Build a reviewer packet

Review @pydantic-ai using the copied upstream files plus provenance, then summarize any gaps before merge.

Explanation: This is useful when the PR is waiting for human review and you want a repeatable audit packet.

Imported Usage Notes

Imported: Examples

Example 1: Code Review Agent

from pydantic import BaseModel, Field
from pydantic_ai import Agent
from typing import Literal

class CodeReview(BaseModel):
    quality: Literal['excellent', 'good', 'needs_work', 'poor']
    issues: list[str] = Field(default_factory=list)
    suggestions: list[str] = Field(default_factory=list)
    approved: bool

code_review_agent = Agent(
    'anthropic:claude-sonnet-4-6',
    result_type=CodeReview,
    system_prompt="""
    You are a senior engineer performing code review.
    Evaluate code quality, identify issues, and provide actionable suggestions.
    Set approved=True only for good or excellent quality code with no security issues.
    """,
)

def review_code(diff: str) -> CodeReview:
    result = code_review_agent.run_sync(f"Review this code:\n\n{diff}")
    return result.data

Example 2: Agent with Retry Logic

from pydantic_ai import Agent, ModelRetry
from pydantic import BaseModel, field_validator

class StrictJson(BaseModel):
    value: int

    @field_validator('value')
    def must_be_positive(cls, v):
        if v <= 0:
            raise ValueError('value must be positive')
        return v

agent = Agent('openai:gpt-4o-mini', result_type=StrictJson)

@agent.result_validator
async def validate_result(ctx, result: StrictJson) -> StrictJson:
    if result.value > 1000:
        raise ModelRetry('Value must be under 1000. Try again with a smaller number.')
    return result

Example 3: Multi-Agent Pipeline

from pydantic_ai import Agent
from pydantic import BaseModel

class ResearchSummary(BaseModel):
    key_points: list[str]
    conclusion: str

class BlogPost(BaseModel):
    title: str
    body: str
    meta_description: str

researcher = Agent('openai:gpt-4o', result_type=ResearchSummary)
writer = Agent('anthropic:claude-sonnet-4-6', result_type=BlogPost)

async def research_and_write(topic: str) -> BlogPost:
    # Stage 1: research
    research = await researcher.run(f'Research the topic: {topic}')

    # Stage 2: write based on research
    post = await writer.run(
        f'Write a blog post about: {topic}\n\nResearch:\n' +
        '\n'.join(f'- {p}' for p in research.data.key_points) +
        f'\n\nConclusion: {research.data.conclusion}'
    )
    return post.data

Best Practices

Treat the generated public skill as a reviewable packaging layer around the upstream repository. The goal is to keep provenance explicit and load only the copied source material that materially improves execution.

• ✅ Always define result_type with a Pydantic model — avoid returning raw strings in production
• ✅ Use deps_type with a dataclass for dependency injection — makes agents testable
• ✅ Use TestModel in unit tests — never hit a real LLM in CI
• ✅ Add @agent.result_validator for business-logic checks beyond Pydantic validation
• ✅ Use run_stream for long outputs in user-facing applications to show progressive results
• ❌ Don't put secrets (API keys) in Agent() arguments — use environment variables
• ❌ Don't share a single Agent instance across async tasks if deps differ — create per-request instances or use agent.run() with per-call deps

Imported Operating Notes

Imported: Best Practices

• ✅ Always define

  result_type

  with a Pydantic model — avoid returning raw strings in production
• ✅ Use

  deps_type

  with a dataclass for dependency injection — makes agents testable
• ✅ Use

  TestModel

  in unit tests — never hit a real LLM in CI
• ✅ Add

  @agent.result_validator

  for business-logic checks beyond Pydantic validation
• ✅ Use

  run_stream

  for long outputs in user-facing applications to show progressive results
• ❌ Don't put secrets (API keys) in

  Agent()

  arguments — use environment variables
• ❌ Don't share a single

  Agent

  instance across async tasks if deps differ — create per-request instances or use

  agent.run()

  with per-call

  deps

• ❌ Don't catch

  ValidationError

  broadly — let PydanticAI retry with

  ModelRetry

  for recoverable LLM output errors

Troubleshooting

Problem: The operator skipped the imported context and answered too generically

Symptoms: The result ignores the upstream workflow in

plugins/antigravity-awesome-skills-claude/skills/pydantic-ai

metadata.json

ORIGIN.md

Problem: The imported workflow feels incomplete during review

Symptoms: Reviewers can see the generated

SKILL.md

Problem: The task drifted into a different specialization

Symptoms: The imported skill starts in the right place, but the work turns into debugging, architecture, design, security, or release orchestration that a native skill handles better. Solution: Use the related skills section to hand off deliberately. Keep the imported provenance visible so the next skill inherits the right context instead of starting blind.

Related Skills

• @prompt-engineer

  - Use when the work is better handled by that native specialization after this imported skill establishes context.

• @prompt-engineering

  - Use when the work is better handled by that native specialization after this imported skill establishes context.

• @prompt-engineering-patterns

  - Use when the work is better handled by that native specialization after this imported skill establishes context.

• @prompt-library

  - Use when the work is better handled by that native specialization after this imported skill establishes context.

Additional Resources

Use this support matrix and the linked files below as the operator packet for this imported skill. They should reflect real copied source material, not generic scaffolding.

references

references/n/a

examples

examples/n/a

scripts

scripts/n/a

agents

agents/n/a

assets

assets/n/a

Imported Reference Notes

Imported: Security & Safety Notes

• Set API keys via environment variables (

  OPENAI_API_KEY

  ,

  ANTHROPIC_API_KEY

  , etc.) — never hardcode them.
• Validate all tool inputs before passing to external systems — use Pydantic models or manual checks.
• Tools that mutate data (write to DB, send emails, call payment APIs) should require explicit user confirmation before the agent invokes them in production.
• Log

  result.all_messages()

  for audit trails when agents perform consequential actions.
• Set

  retries=

  limits on

  Agent()

  to prevent runaway loops on persistent validation failures.

Imported: Common Pitfalls

• Problem:

  ValidationError

  on every LLM response — structured output never validates Solution: Simplify

  result_type

  fields. Use

  Optional

  and

  default

  where appropriate. The model may struggle with overly strict schemas.

• Problem: Tool is never called by the LLM Solution: Write a clear, specific docstring for the tool function — PydanticAI sends the docstring as the tool description to the LLM.

• Problem:

  RunContext

  dependency is

  None

  inside a tool Solution: Pass

  deps=

  when calling

  agent.run()

  or

  agent.run_sync()

  . Dependencies are not set globally.

• Problem:

  asyncio.run()

  error when calling

  agent.run()

  inside FastAPI Solution: Use

  await agent.run()

  directly in async FastAPI route handlers — don't wrap in

  asyncio.run()

  .

Imported: Limitations

• Use this skill only when the task clearly matches the scope described above.
• Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
• Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.