fastmcp.apps.form

FormInput — a Provider that collects structured input from the user.

Define a Pydantic model for the data you need, and FormInput generates a form UI. The user fills it out, the submission is validated, and an optional callback processes the result.

Requires fastmcp[apps] (prefab-ui).

Usage::

from pydantic import BaseModel
from fastmcp import FastMCP
from fastmcp.apps.form import FormInput

class ShippingAddress(BaseModel):
    street: str
    city: str
    state: str
    zip_code: str

mcp = FastMCP("My Server")
mcp.add_provider(FormInput(model=ShippingAddress))

Classes

FormInput ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/apps/form.py#L78" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

A Provider that collects structured input via a Pydantic model.

Define a model for the data you need, and FormInput generates a form from it using Form.from_model(). Field types, labels, descriptions, and validation are all derived from the model.

Optionally provide an on_submit callback to process the validated data. The callback receives a model instance and returns a string that goes back to the LLM. Without a callback, the validated JSON is sent directly.

Example::

from pydantic import BaseModel
from fastmcp import FastMCP
from fastmcp.apps.form import FormInput

class Contact(BaseModel):
    name: str
    email: str

mcp = FastMCP("My Server")
mcp.add_provider(FormInput(model=Contact))

With a callback::

def save_contact(contact: Contact) -> str:
    db.insert(contact.model_dump())
    return f"Saved {contact.name}"

mcp.add_provider(FormInput(model=Contact, on_submit=save_contact))