> ## Documentation Index > Fetch the complete documentation index at: https://docs.major.build/llms.txt > Use this file to discover all available pages before exploring further. # Nodes > Every workflow node type, its fields, and the rules a workflow graph must follow. A workflow's `nodes` are its steps and its `edges` connect them. Every node has an `id`, a `type`, a `config`, and an optional `label` that's shown in the graph. This page lists each node type's `config` fields. The authoritative definition is the JSON Schema at `https://api.prod.major.build/public/workflow.schema.json`. Use underscores, not hyphens, in node ids. A hyphenated id can't be referenced from a `$expr` expression. ## agent\_call Runs an [agent](/learn/agents/overview) with a prompt. | Field | Required | Description | | - | - | - | | `agent_id` | Yes | The agent to run. | | `prompt` | Yes | The instruction sent to the agent. Supports `{{ }}` interpolation. | | `output_schema` | No | A JSON Schema for the agent's answer. With it, the node's output has exactly that shape. Without it, the output is `{ "result": "" }`. | | `approval_channel` | No | `{ "type": "slack", "channel_id": "...", "channel_name": "..." }`. Sends the agent's [tool approval](/learn/agents/tool-permissions) requests to a Slack channel instead of the app. | ## app\_call Calls an endpoint on one of your deployed [apps](/learn/apps/overview). | Field | Required | Description | | - | - | - | | `app_id` | Yes | The app to call. | | `method` | Yes | `GET`, `POST`, `PUT`, `PATCH`, or `DELETE`. | | `path` | Yes | The endpoint path, for example `/api/orders`. | | `input` | No | An object of values. Sent as query parameters for `GET` and `DELETE`, and as a JSON body otherwise. | The node's output is the response body. A body that isn't a JSON object is wrapped as `{ "body": ... }`. ## router Branches the run on state. | Field | Required | Description | | - | - | - | | `branches` | Yes | A list of `{ "when": { "$expr": "..." }, "to": ["node_id", ...], "label": "..." }`. | | `default` | Yes | Node ids to run when no branch matches. | | `default_label` | No | Label for the default path in the graph. | Branches are checked top to bottom and the first one whose `when` is true wins. A condition that evaluates to `null` doesn't match. Every target in the winning `to` list runs in parallel. The router must have exactly one outgoing edge per target named in its branches and default. ## for\_each Runs a loop body once per item in a list. | Field | Required | Description | | - | - | - | | `input.iterable` | Yes | The list to loop over, usually a `$state` or `$expr` reference. | | `mode` | No | `sequential` (default) or `parallel`. | | `max_concurrency` | No | Upper bound on parallel iterations. | | `max_iterations` | No | Upper bound on the number of iterations. | | `collect_results` | No | Defaults to `true`. Set to `false` to skip collecting results. | A `for_each` has two outgoing edges: one with `"loop": "body"` into the loop body, and one with `"loop": "exit"` that runs after the last iteration. Every path from the body must lead back to the `for_each`. Loop bodies are the only cycles a workflow may have. Inside the body, `.item` and `.index` are the current item and its position. After the exit edge, `.results` holds each iteration's final output, in item order. ## join Waits for parallel branches to meet. | Field | Required | Description | | - | - | - | | `mode` | Yes | `all`. The join releases once every inbound edge has arrived. | Every edge into a join must come from the same fan-out (a `router` branch with several targets, for example), with no other join in between. Keep each parallel leg a simple line into the join. ## wait Pauses the run. | Field | Required | Description | | - | - | - | | `duration_seconds` | Yes | How long to wait, in seconds. | ## human\_approval Asks a person to choose in Slack. Requires the Major Slack integration. | Field | Required | Description | | - | - | - | | `channel` | Yes | `{ "type": "slack", "channel_id": "..." }`. | | `message` | Yes | The message to post. Supports `{{ }}` interpolation. | | `options` | Yes | Buttons, each `{ "value": "...", "label": "...", "style": "..." }`. `value` is required; `style` is `primary`, `danger`, or `neutral`. | | `timeout_seconds` | No | How long to wait for a click. | | `on_timeout` | With a timeout | The option `value` to use if no one answers in time. Required when `timeout_seconds` is set. | | `reminder_interval_seconds` | No | Post a reminder at this interval while waiting. | The output is `{ "choice": "", "responded_by": "" }`, or `{ "choice": "", "timed_out": true }` on timeout. A `human_approval` has one outgoing edge, which should lead to a `router` that branches on `.choice`. Only Major members with access to the workflow can answer. ## end Finishes the run. | Field | Required | Description | | - | - | - | | `status` | No | `success` (default) or `failure`. | | `output` | No | An object of values to record as the run's output. | An `end` node has no outgoing edges. ## Edges Each edge is `{ "id": "...", "from": "node_id", "to": "node_id" }`, with an optional `label` shown in the graph. Only `for_each` out-edges carry `"loop": "body"` or `"loop": "exit"`. ## Graph rules Saving checks the definition against these rules, and errors name the path that failed: * At most 50 nodes, and the file is at most 256 KB. * Node ids and edge ids are unique. `trigger` is reserved and can't be a node id. * `entry` and every edge's `from` and `to` name an existing node. * Only `router` and `for_each` fan out. Every other node has exactly one outgoing edge, and `end` nodes have none. * A node can have several inbound edges only if at most one of them can be active at a time. Parallel paths must meet at a `join` first. * Every node is reachable from `entry`, and every path reaches an `end` node or loops back to a `for_each`. ## Next steps Reference node outputs and workflow input. Start the workflow automatically.