Write a flow

This page builds acme.process-order: look an order up, have an agent write a thank-you note, then confirm the order with that note. Two tools, one agent, one flow.

The tools

Ask your coding agent: "I want a tool that looks up an order, and one that confirms an order with a note." Kindgi's skills in your pack tell it how (How it knows Kindgi). For reference, the tools look like this. acme.get-order only reads, so it says mutating: false. acme.confirm-order changes something, so it doesn't:

TypeScript

tools/get-order/index.ts

import { defineTool } from '@kindgi/sdk/define';
import type { ToolId } from '@kindgi/sdk/types';
import { z } from 'zod';

const Order = z.object({
  orderId: z.string(),
  customer: z.string(),
  total: z.number(),
  items: z.array(z.object({ sku: z.string(), quantity: z.number().int() })),
});

const ORDERS: Record<string, z.infer<typeof Order>> = {
  'A-100': { orderId: 'A-100', customer: 'ada@example.com', total: 42.5, items: [{ sku: 'mug', quantity: 2 }] },
  'A-200': {
    orderId: 'A-200',
    customer: 'grace@example.com',
    total: 1250,
    items: [
      { sku: 'desk', quantity: 1 },
      { sku: 'lamp', quantity: 2 },
    ],
  },
};

const defined = defineTool({
  id: 'acme.get-order' as ToolId,
  description: 'Looks up an order by id.',
  version: '0.1.0',
  input: z.object({ orderId: z.string().min(1) }),
  output: Order,
  effects: [],
  mutating: false, // only reads
  handler: async ({ orderId }) => {
    const order = ORDERS[orderId];
    if (order === undefined) throw new Error(`No order ${orderId}`);
    return order;
  },
});

if (defined.kind === 'err') throw new Error(defined.error.message);

export default defined.value;

tools/confirm-order/index.ts

import { defineTool } from '@kindgi/sdk/define';
import type { ToolId } from '@kindgi/sdk/types';
import { z } from 'zod';

const defined = defineTool({
  id: 'acme.confirm-order' as ToolId,
  description: 'Confirms an order and emails the customer.',
  version: '0.1.0',
  input: z.object({ orderId: z.string(), note: z.string().optional() }),
  output: z.object({
    orderId: z.string(),
    status: z.literal('confirmed'),
    note: z.string().optional(),
  }),
  effects: [],
  // no `mutating: false`: it changes something
  handler: async ({ orderId, note }) => ({ orderId, status: 'confirmed' as const, note }),
});

if (defined.kind === 'err') throw new Error(defined.error.message);

export default defined.value;

Python

tools/get_order.py

from pydantic import BaseModel, Field

from kindgi import tool


class OrderQuery(BaseModel):
    order_id: str = Field(alias="orderId", min_length=1)


class Item(BaseModel):
    sku: str
    quantity: int


class Order(BaseModel):
    order_id: str = Field(alias="orderId")
    customer: str
    total: float
    items: list[Item]


ORDERS = {
    "A-100": {"customer": "ada@example.com", "total": 42.5, "items": [{"sku": "mug", "quantity": 2}]},
    "A-200": {
        "customer": "grace@example.com",
        "total": 1250,
        "items": [{"sku": "desk", "quantity": 1}, {"sku": "lamp", "quantity": 2}],
    },
}


@tool(id="acme.get-order", mutating=False)  # only reads
def get_order(input: OrderQuery) -> Order:
    """Looks up an order by id."""
    order = ORDERS.get(input.order_id)
    if order is None:
        raise ValueError(f"No order {input.order_id}")
    return Order(orderId=input.order_id, **order)

tools/confirm_order.py

from typing import Literal

from pydantic import BaseModel, Field

from kindgi import tool


class ConfirmInput(BaseModel):
    order_id: str = Field(alias="orderId")
    note: str | None = None


class Confirmed(BaseModel):
    order_id: str = Field(alias="orderId")
    status: Literal["confirmed"] = "confirmed"
    note: str | None = None


@tool(id="acme.confirm-order")  # no mutating=False: it changes something
def confirm_order(input: ConfirmInput) -> Confirmed:
    """Confirms an order and emails the customer."""
    return Confirmed(orderId=input.order_id, note=input.note)

Java

src/main/java/acme/tools/GetOrder.java

package acme.tools;

import com.kindgi.pack.Tool;
import jakarta.validation.constraints.Size;
import java.util.List;
import java.util.Map;

public final class GetOrder {
  public record Input(@Size(min = 1) String orderId) {}

  public record Item(String sku, int quantity) {}

  public record Order(String orderId, String customer, double total, List<Item> items) {}

  private static final Map<String, Order> ORDERS = Map.of(
      "A-100", new Order("A-100", "ada@example.com", 42.5, List.of(new Item("mug", 2))),
      "A-200", new Order("A-200", "grace@example.com", 1250,
          List.of(new Item("desk", 1), new Item("lamp", 2))));

  public static final Tool<Input, Order> TOOL = Tool.define("acme.get-order")
      .description("Looks up an order by id.")
      .version("0.1.0")
      .input(Input.class)
      .output(Order.class)
      .mutating(false) // only reads
      .handler((input, ctx) -> {
        Order order = ORDERS.get(input.orderId());
        if (order == null) throw new IllegalArgumentException("No order " + input.orderId());
        return order;
      });

  private GetOrder() {}
}

src/main/java/acme/tools/ConfirmOrder.java

package acme.tools;

import com.fasterxml.jackson.annotation.JsonProperty;
import com.kindgi.pack.Tool;
import org.jspecify.annotations.Nullable;

public final class ConfirmOrder {
  public record Input(String orderId, @Nullable String note) {}

  public enum Status {
    @JsonProperty("confirmed") CONFIRMED
  }

  public record Confirmed(String orderId, Status status, @Nullable String note) {}

  public static final Tool<Input, Confirmed> TOOL = Tool.define("acme.confirm-order")
      .description("Confirms an order and emails the customer.")
      .version("0.1.0")
      .input(Input.class)
      .output(Confirmed.class)
      // no mutating(false): it changes something
      .handler((input, ctx) -> new Confirmed(input.orderId(), Status.CONFIRMED, input.note()));

  private ConfirmOrder() {}
}

Scala

src/main/scala/acme/tools/GetOrder.scala

package acme.tools

import com.kindgi.pack.scaladsl._
import jakarta.validation.constraints.Size

object GetOrder {
  final case class Input(@Size(min = 1) orderId: String)
  final case class Item(sku: String, quantity: Int)
  final case class Order(orderId: String, customer: String, total: Double, items: Seq[Item])

  private val orders = Map(
    "A-100" -> Order("A-100", "ada@example.com", 42.5, Seq(Item("mug", 2))),
    "A-200" -> Order("A-200", "grace@example.com", 1250, Seq(Item("desk", 1), Item("lamp", 2))))

  val tool: Tool[Input, Order] = Tool[Input, Order]("acme.get-order")
    .description("Looks up an order by id.")
    .version("0.1.0")
    .readOnly // only reads
    .handler((in, _) =>
      orders.getOrElse(in.orderId, throw new NoSuchElementException(s"No order ${in.orderId}")))
}

src/main/scala/acme/tools/ConfirmOrder.scala

package acme.tools

import com.kindgi.pack.scaladsl._

object ConfirmOrder {
  final case class Input(orderId: String, note: Option[String])

  enum Status {
    case confirmed
  }

  final case class Confirmed(orderId: String, status: Status, note: Option[String])

  val tool: Tool[Input, Confirmed] = Tool[Input, Confirmed]("acme.confirm-order")
    .description("Confirms an order and emails the customer.")
    .version("0.1.0")
    // no readOnly: it changes something
    .handler((in, _) => Confirmed(in.orderId, Status.confirmed, in.note))
}

The agent

Ask your coding agent: "I want an agent that writes a one-sentence thank-you note for an order." For reference, the agent looks like this. It has no tools: it reads the order's customer and total from its input and answers with one sentence:

TypeScript

agents/note-writer/index.ts

import { defineAgent } from '@kindgi/sdk/define';
import type { AgentId, Semver } from '@kindgi/sdk/types';

const defined = defineAgent({
  id: 'acme.note-writer' as AgentId,
  version: '0.1.0' as Semver,
  name: 'Note writer',
  description: 'Writes a one-sentence thank-you note for an order.',
  instructions:
    'Write a one-sentence thank-you note to {{ input.customer }} for their order of {{ input.total }} USD. Answer with the note only.',
  capabilities: [{ needs: [{ feature: 'tool-use' as const }] }],
  tools: [],
  retrieval: [],
  guardrails: [],
  parameters: [],
  budget: { maxSteps: 2, maxCostUsd: 0.05, maxWallMs: 30_000 },
});

if (defined.kind === 'err') throw new Error(defined.error.message);

export default defined.value;

Python

agents/note_writer.py

from kindgi import Agent

note_writer = Agent(
    id="acme.note-writer",
    version="0.1.0",
    name="Note writer",
    description="Writes a one-sentence thank-you note for an order.",
    instructions=(
        "Write a one-sentence thank-you note to {{ input.customer }} for their order of "
        "{{ input.total }} USD. Answer with the note only."
    ),
    capabilities=[{"needs": [{"feature": "tool-use"}]}],
    budget={"maxSteps": 2, "maxCostUsd": 0.05, "maxWallMs": 30_000},
)

Java

src/main/java/acme/agents/NoteWriter.java

package acme.agents;

import com.kindgi.pack.Agent;
import java.util.List;
import java.util.Map;

public final class NoteWriter {
  public static final Agent AGENT = Agent.define("acme.note-writer")
      .version("0.1.0")
      .name("Note writer")
      .description("Writes a one-sentence thank-you note for an order.")
      .instructions("Write a one-sentence thank-you note to {{ input.customer }} for their order of "
          + "{{ input.total }} USD. Answer with the note only.")
      .capability(Map.of("needs", List.of(Map.of("feature", "tool-use"))))
      .set("budget", Map.of("maxSteps", 2, "maxCostUsd", 0.05, "maxWallMs", 30_000))
      .build();

  private NoteWriter() {}
}

Scala

src/main/scala/acme/agents/NoteWriter.scala

package acme.agents

import com.kindgi.pack.scaladsl._

object NoteWriter {
  val agent: Agent = Agent("acme.note-writer")
    .version("0.1.0")
    .name("Note writer")
    .description("Writes a one-sentence thank-you note for an order.")
    .instructions("Write a one-sentence thank-you note to {{ input.customer }} for their order of " +
      "{{ input.total }} USD. Answer with the note only.")
    .capability(Map("needs" -> Seq(Map("feature" -> "tool-use"))))
    .set("budget", Map("maxSteps" -> 2, "maxCostUsd" -> 0.05, "maxWallMs" -> 30000))
    .build()
}

The flow

Ask your coding agent: "I want a flow that looks up an order, has the agent write a thank-you note, then confirms the order with that note." For reference, the flow looks like this:

TypeScript

flows/process-order/index.ts

import { defineFlow } from '@kindgi/sdk/define';

const defined = defineFlow({
  id: 'acme.process-order',
  version: '0.1.0',
  name: 'Process an order',
  description: 'Looks up an order, writes a thank-you note, and confirms the order with it.',
  nodes: [
    {
      id: 'order',
      kind: 'tool',
      ref: 'acme.get-order',
      inputMapping: { orderId: { path: 'runInput.orderId' } },
    },
    {
      id: 'note',
      kind: 'agent',
      ref: 'acme.note-writer',
      inputMapping: {
        customer: { path: 'nodeOutputs.order.customer' },
        total: { path: 'nodeOutputs.order.total' },
      },
    },
    {
      id: 'confirm',
      kind: 'tool',
      ref: 'acme.confirm-order',
      inputMapping: {
        orderId: { path: 'runInput.orderId' },
        note: { path: 'nodeOutputs.note.text' },
      },
    },
  ],
  edges: [
    { id: 'e1', from: '$start', to: 'order' },
    { id: 'e2', from: 'order', to: 'note' },
    { id: 'e3', from: 'note', to: 'confirm' },
    { id: 'e4', from: 'confirm', to: '$end' },
  ],
});

if (defined.kind === 'err') throw new Error(defined.error.message);

export default defined.value;

Python

flows/process_order.py

from kindgi import Flow

process_order = Flow(
    id="acme.process-order",
    version="0.1.0",
    name="Process an order",
    description="Looks up an order, writes a thank-you note, and confirms the order with it.",
    nodes=[
        {
            "id": "order",
            "kind": "tool",
            "ref": "acme.get-order",
            "inputMapping": {"orderId": {"path": "runInput.orderId"}},
        },
        {
            "id": "note",
            "kind": "agent",
            "ref": "acme.note-writer",
            "inputMapping": {
                "customer": {"path": "nodeOutputs.order.customer"},
                "total": {"path": "nodeOutputs.order.total"},
            },
        },
        {
            "id": "confirm",
            "kind": "tool",
            "ref": "acme.confirm-order",
            "inputMapping": {
                "orderId": {"path": "runInput.orderId"},
                "note": {"path": "nodeOutputs.note.text"},
            },
        },
    ],
    edges=[
        {"id": "e1", "from": "$start", "to": "order"},
        {"id": "e2", "from": "order", "to": "note"},
        {"id": "e3", "from": "note", "to": "confirm"},
        {"id": "e4", "from": "confirm", "to": "$end"},
    ],
)

Java

src/main/java/acme/flows/ProcessOrder.java

package acme.flows;

import acme.agents.NoteWriter;
import acme.tools.ConfirmOrder;
import acme.tools.GetOrder;
import com.kindgi.pack.Flow;
import java.util.Map;

public final class ProcessOrder {
  public static final Flow FLOW = Flow.define("acme.process-order")
      .version("0.1.0")
      .set("name", "Process an order")
      .set("description", "Looks up an order, writes a thank-you note, and confirms the order with it.")
      .node(Map.of(
          "id", "order",
          "kind", "tool",
          "ref", GetOrder.TOOL,
          "inputMapping", Map.of("orderId", Map.of("path", "runInput.orderId"))))
      .node(Map.of(
          "id", "note",
          "kind", "agent",
          "ref", NoteWriter.AGENT,
          "inputMapping", Map.of(
              "customer", Map.of("path", "nodeOutputs.order.customer"),
              "total", Map.of("path", "nodeOutputs.order.total"))))
      .node(Map.of(
          "id", "confirm",
          "kind", "tool",
          "ref", ConfirmOrder.TOOL,
          "inputMapping", Map.of(
              "orderId", Map.of("path", "runInput.orderId"),
              "note", Map.of("path", "nodeOutputs.note.text"))))
      .edge("e1", "$start", "order")
      .edge("e2", "order", "note")
      .edge("e3", "note", "confirm")
      .edge("e4", "confirm", "$end")
      .build();

  private ProcessOrder() {}
}

A step with no inputMapping can be shorter: .toolNode("order", GetOrder.TOOL) or .agentNode("note", NoteWriter.AGENT).

Scala

src/main/scala/acme/flows/ProcessOrder.scala

package acme.flows

import acme.agents.NoteWriter
import acme.tools.{ConfirmOrder, GetOrder}
import com.kindgi.pack.scaladsl._

object ProcessOrder {
  val flow: Flow = Flow("acme.process-order")
    .version("0.1.0")
    .set("name", "Process an order")
    .set("description", "Looks up an order, writes a thank-you note, and confirms the order with it.")
    .node(Map(
      "id" -> "order",
      "kind" -> "tool",
      "ref" -> GetOrder.tool,
      "inputMapping" -> Map("orderId" -> Map("path" -> "runInput.orderId"))))
    .node(Map(
      "id" -> "note",
      "kind" -> "agent",
      "ref" -> NoteWriter.agent,
      "inputMapping" -> Map(
        "customer" -> Map("path" -> "nodeOutputs.order.customer"),
        "total" -> Map("path" -> "nodeOutputs.order.total"))))
    .node(Map(
      "id" -> "confirm",
      "kind" -> "tool",
      "ref" -> ConfirmOrder.tool,
      "inputMapping" -> Map(
        "orderId" -> Map("path" -> "runInput.orderId"),
        "note" -> Map("path" -> "nodeOutputs.note.text"))))
    .edge("e1", "$start", "order")
    .edge("e2", "order", "note")
    .edge("e3", "note", "confirm")
    .edge("e4", "confirm", "$end")
    .build()
}

• nodes are the steps. Each has an id (unique in the flow), a kind and a ref: the id of the tool or agent it runs. In Python, Java and Scala, ref can also be the tool or agent itself.
• edges connect them. $start and $end are where the run enters and leaves; an edge without a condition fires when its source step completes.
• inputMapping builds each step's input from the run's input (runInput.…) and earlier steps' outputs (nodeOutputs.<step>.…). See Pass data between steps.

The shape is checked when the file loads: ids, edges between steps that exist, $start and $end, no cycles. That the tools and the agent exist is checked when a run starts: a run of a flow that names a tool your tenant doesn't have is refused before anything runs.

Run it

With kindgi dev running in the pack, start a run from a second terminal:

TypeScript

pnpm exec kindgi runs start --flow=acme.process-order --input='{"orderId":"A-100"}'

Python

uv run kindgi runs start --flow=acme.process-order --input='{"orderId":"A-100"}'

Java

./kindgiw runs start --flow=acme.process-order --input='{"orderId":"A-100"}'

Scala

./kindgiw runs start --flow=acme.process-order --input='{"orderId":"A-100"}'

{
  "id": "f35d0699-00d8-4e85-944c-e0c9da3ce8e5",
  …
  "flowId": "acme.process-order",
  "flowVersion": "0.1.0",
  "status": "completed",
  "dryRun": false,
  …
  "output": {
    "note": "Thank you for your order of $42.50, ada@example.com!",
    "status": "confirmed",
    "orderId": "A-100"
  },
  …
}

Excerpt

The command waits for the run to finish. The flow declares no output, so the run returns the output of the step that reached $end: here, acme.confirm-order's.

The agent step

An agent step runs one turn of the agent, as a run of its own (a child of the flow's run). The agent gets the step's input twice: as structured input, which {{ input.customer }} in its instructions reads, and as its user message (the input as JSON). Give an agent its input has the details.

The step's output has the answer as text, and as output when the agent declares a typed answer, plus the turn's runId. Without a model provider, dev-echo answers, and the note is the agent's input echoed back.

Change it

Save a file and kindgi dev loads the new version; the next run uses it, with no restart. A run already in flight keeps the version it started on. Change version when what callers send or get back changes, not on every save.

In the console

A project's Flows page lists its flows: "A flow runs agents and tools as its steps: in order, side by side or repeated, all in one run. Each flow is shown at its latest version; retired ones last." Each row has the flow's name and description, its latest version, what it runs ("3 steps: 2 agents, 1 repeating step") and its agent and tool versions ("Locked when published"). A flow whose every version is retired is marked retired. The list has a search box, sorts by a column's header, and Columns chooses which columns it shows.

A flow's page has Runs and Cost at the top, and Start run while a version is in use, only to people who may run the flow. It says which version it shows: "2.0.0 (its latest): 3 steps: 2 agents, 1 repeating step." It draws that version as a graph, from Start to End: each step with what it runs, by name, and at which version, such as "locked at 1.0.0", and a repeating step in words ("For each item of the run's items, at most 50 times: Dev-Echo Agent"). Below it:

• What 2.0.0 uses: its agents and tools, each with what it does and its version: "Locked when this version was published: every run of it uses these versions."
• Versions: "Runs use the latest unless they name a version." Every version is listed, a retired one marked retired, each with what it runs and Runs →, the runs list filtered to that version.
• What triggers it: the schedules, incoming webhooks and mail triggers that start it, each with the version it starts, such as "Schedule: Every day at 2:00 AM UTC · version 2.0.0" or "Mail trigger: new mail in the company's Gmail, inbox · version 2.0.0". With none, it says "No schedule, incoming webhook or mail trigger: people and apps start it."

For flow admins, each version in use has Retire: the archive icon at the row's end, with the word only on hover. It asks first, saying what changes:

Retire 1.0.0?
Runs that name no version keep using 2.0.0.
Runs that name 1.0.0 are refused, a schedule's included; runs already going finish. It stays listed here as retired, with Bring back.

Retiring the latest says which version runs that name none use instead, such as "Runs that name no version use 1.1.0 instead." While the dialog is still open, Bring it back undoes it. Later, the version's row has Bring back, and the version's own page says "1.0.0 is retired", since when, and "Runs that name it are refused, and runs that name no version don't use it.", with Bring back.

Retiring a flow's only version in use says "It is the only version in use: the Flows list shows the flow as retired, and runs that name no version are refused until a version is brought back or published." Its page then says "Every version of this flow is retired": "The Flows list shows it as retired, and runs that name no version are refused. Bring a version back under Versions, or publish a new one."

Under kindgi dev, Retire and Bring back are off: "the pack's files are this flow's versions. Change the flow there, and kindgi dev reloads it."

Next

• Pass data between steps
• Branch a flow
• Start a run from your app