# Reasoning and Tool Calls Before an agent answers, it often reasons, and it may call tools: search the web, look up an order, or ask the user's device for their location. StreamChatAI shows these steps in the reply, in the order they happened, with the final answer after them. An agent describes each step as a custom attachment on its reply message: - `ai_reasoning` - a round of the model's reasoning. - `ai_tool_call` - a tool the agent called, run by the agent's backend or by a user's device. The order of the attachments is the order of the steps, and the final answer stays in the message text. The agent's backend adds the steps to the reply's `attachments` and updates them as it works, with the same message updates that stream the text. > > **Info:** The views and types on this page are part of StreamChatAI, available from version 5.13.0 of the Stream Chat Swift SDK. See [Installation](https://getstream.io/chat/docs/sdk/ios/guides/ai-integrations/#installation). > ## Show the steps of a reply `AIMessagePart` decodes the steps among a message's attachments, skipping attachments that aren't AI steps, such as images. `AIMessagePartsView` shows them in order. Render it before the reply's text: ```swift let parts = AIMessagePart.parts( from: message.allAttachments.map { ($0.type.rawValue, $0.payload) } ) VStack(alignment: .leading) { AIMessagePartsView(parts: parts) StreamingMessageView(content: message.text, isGenerating: isGenerating) } ``` Each step shows through `AIMessagePartView`: a round of reasoning as a `StreamingReasoningView`, a tool call as an `AIToolCallView`, and a neutral placeholder ("A step this app version can't show") for a kind of step it doesn't know. The [SwiftUI integration](https://getstream.io/chat/docs/sdk/ios/guides/ai-integrations/swiftui-integration/) shows where to render it in the Chat SDK's message list. ### Steps are an open set New kinds of steps can appear without breaking your code. A part's `kind` is a string-backed value (`.reasoning`, `.toolCall`, or any other `ai_` attachment type), and the kinds the SDK reads have typed views, `part.reasoning` and `part.toolCall`. Anything else keeps its JSON `payload`, which you can read with `part.decode(_:)`. Statuses and executors are open in the same way, so switch over them with a `default`. Decoding is lenient: missing fields get defaults, a field of the wrong type reads as missing, and a step in a newer format version (`v`) keeps its payload but has no typed view. Each step has a stable `id` (a tool call uses the model provider's tool-call ID), so the list updates smoothly while it streams. To show some steps your own way, such as reasoning your backend streams in full, or a kind of step of your own, render each part yourself and fall back to `AIMessagePartView` for the rest: ```swift AIMessagePartsView(parts: parts) { part in if let reasoning = part.reasoning { StreamingReasoningView(part: reasoning, text: fullReasoning[reasoning.id]) } else if part.kind == "ai_citation", let citation = try? part.decode(Citation.self) { CitationView(citation: citation) } else { AIMessagePartView(part: part) } } ``` ## Reasoning A round of reasoning carries a capped `preview` of the model's thoughts (the latest ones while it streams, the opening once it's done) and a one-line `summary`. `AIMessagePartView` shows it with `StreamingReasoningView`: while the model thinks, the reasoning streams into an open panel under a "Thinking... 7s" header, and once it's done, the view folds into "Thought for 12s" and the summary. Tapping the header opens or closes the reasoning. You can also use `StreamingReasoningView` on its own, with reasoning you get some other way, for example streamed from your backend: ```swift StreamingReasoningView( text: reasoning, isThinking: answer.isEmpty, duration: thinkingDuration ) ``` Reasoning can run to tens of kilobytes and grow many times a second, so the view only lays out what changes: it renders one paragraph at a time, lazily, so only the paragraph still being written is laid out again. Blank lines separate paragraphs, and inline Markdown (bold, italics, code and links) is rendered. | Parameter | Description | Default | | -------------------- | ---------------------------------------------------------------------------- | -------------------------------- | | `text` | The reasoning so far. | - | | `isThinking` | Whether the model is still thinking. While it is, the header counts seconds. | - | | `duration` | How long the model thought, shown as "Thought for 12s" once it's done. | `nil` | | `summary` | A one-line summary shown beside the header once the model is done. | `nil` | | `footnote` | A note under the open reasoning, such as how long it's kept. | `nil` | | `initiallyExpanded` | Whether the reasoning is open once the model is done. | `false` | | `showsLiveReasoning` | Whether the reasoning is open while the model thinks. | `true` | | `maxExpandedHeight` | How tall the reasoning grows before it scrolls. | `260` | | `font` | The font of the reasoning. The header uses it in a medium weight. | `AIAppearance.fonts.messagePart` | Once the reader opens or closes the reasoning themselves, the view keeps their choice. `StreamingReasoningView.foldAnimation` is the animation the view folds and opens with: use it for your own changes that should move along with it. `StreamingReasoningView.foldDuration` is how long the fold takes, so a reply that shows its answer only after it lets the reasoning fold first, rather than the two moving against each other. ## Tool calls `AIToolCallView` shows a single tool call: what it's doing (its `display_title`, such as "Checking your location", or else its name), its outcome (`summary`), and its duration once it's finished. Its icon follows the status: a spinner while it runs, a hand while it waits for approval, a phone while it waits for the user's device, and a checkmark, an exclamation mark or a cross once it completed, failed or was cancelled. ```swift if let call = part.toolCall { AIToolCallView(part: call) } ``` When the agent asks a user's device to run a tool, `AIClientToolRunner` runs it there and sends the result back, as described in [Client Side Tools](https://getstream.io/chat/docs/sdk/ios/guides/ai-integrations/client-side-tools/#run-tool-calls-from-agent-steps). ## Tool approvals Some tool calls should wait for the user: the agent wants their location, or to send an email on their behalf. The agent's backend writes such a call with status `awaiting_approval`, addresses it to that user (`target_user_id`, and `target_client_id` for a client tool), and adds the question as its `approval`: ```json { "type": "ai_tool_call", "id": "toolu_01A", "name": "get_location", "status": "awaiting_approval", "executor": "client", "target_user_id": "u_123", "target_client_id": "ios-7F3A", "approval": { "title": "Share your location?", "message": "Only your city is shared.", "reason": "to check the local weather", "allow_title": "Share location", "decline_title": "Don't share" } } ``` `AIToolApprovalView` asks the question under the call. It shows only to that user, on the install the call names (or on any of their devices, for a server tool), and only while the call waits. Give it an `AIToolApprover`, which says who is signed in on this device and sends their answer to your backend: ```swift let approver = AIToolApprover( userID: currentUserID, clientID: AIClientIdentity.installID ) { call, allowed in try await backend.answer(call, allowed: allowed) } AIToolCallView(part: call) AIToolApprovalView(call: call, approver: approver) ``` Passing the approver to `AIMessagePartsView(parts: parts, approver: approver)` does this for every tool call of the reply. While the answer is on its way, the buttons are disabled. If `decide` throws, the user can answer again. Your backend holds the call until it gets the answer, and accepts one only from the targeted user (and install, for a client tool), only while the call waits, and only once. It then updates the step: - **Allowed:** `approval.decision` becomes `allowed` and the call goes on. A client tool's call moves to `awaiting_client`, so the device's `AIClientToolRunner` runs it. - **Declined:** the call becomes `cancelled`, with `approval.decision` set to `declined`, and never runs. `isDeclined` tells it apart from other cancelled calls, and `AIToolCallView` shows it as "Declined". The question is visible to every channel member, so keep private data out of it. To ask in your own design, pass the content. It gets the question, where the answer is, and a closure that answers: ```swift AIToolApprovalView(call: call, approver: approver) { approval, state, decide in MyApprovalCard( title: approval.title, isBusy: state.isSending, onAllow: { decide(true) }, onDecline: { decide(false) } ) } ``` `AIToolApprovalCard` is the default design. ## Step format The steps are custom attachments, with their fields at the top level of the attachment. Every step has: | Field | Description | | ------ | -------------------------------------------------------------------------------------------- | | `type` | The kind of step: `ai_reasoning`, `ai_tool_call`, or a kind of your own starting with `ai_`. | | `id` | The step's stable identity. Tool calls use the model provider's tool-call ID. | | `v` | The step's format version, `1` by default. It changes only when a kind changes incompatibly. | A round of reasoning (`ai_reasoning`) also has: | Field | Description | | ------------- | ----------------------------------------------------------------------------- | | `status` | `streaming` while the model thinks, or `completed` (the default). | | `summary` | A one-line summary of the reasoning, once it's done. | | `preview` | A capped excerpt: the latest thoughts while streaming, the opening once done. | | `duration_ms` | How long the model thought, in milliseconds. | A tool call (`ai_tool_call`) also has: | Field | Description | | ------------------ | ----------------------------------------------------------------------------------------------------------------------------------- | | `name` | The tool's name. | | `display_title` | What the call is doing, in words for people, such as "Checking your location". | | `status` | `running` (the default), `awaiting_approval`, `awaiting_client`, `completed`, `failed` or `cancelled`. | | `executor` | Who runs the tool: `server` (the default) or `client`. | | `target_user_id` | The user whose device must run a client tool, or who must approve the call. | | `target_client_id` | The install that must run a client tool, copied from the `client_id` in the custom data of the user's message. | | `arguments` | The call's arguments as a JSON object, present for client tools, which need them to run. | | `summary` | A short, shareable outcome, such as "Found your location". | | `duration_ms` | How long the call took, in milliseconds. | | `approval` | The question the call asks before it runs: `title`, `message`, `reason`, `allow_title`, `decline_title`, and the user's `decision`. | Every channel member can see the steps, their arguments and their summaries, so keep private data out of them. ## Appearance The colors of the steps are part of `AIAppearance.colors`: `reasoningTitle`, `reasoningText`, `reasoningFootnote`, `reasoningShimmer` and `reasoningRule` for the reasoning, `toolCallTitle`, `toolCallDetail`, `toolCallAccent`, `toolCallSuccess` and `toolCallFailure` for tool calls, and `toolApprovalTitle`, `toolApprovalMessage`, `toolApprovalBackground`, `toolApprovalBorder`, `toolApprovalAccent` and `toolApprovalFailure` for the approval card. Their fonts are part of `AIAppearance.fonts`: `messagePart` for the steps themselves, `reasoningFootnote`, `toolCallDetail`, and `toolApprovalMessage` and `toolApprovalFailure` for the approval card. Their icons are part of `AIAppearance.images`, and their texts, such as "Waiting for approval" or the default "Allow" and "Don't Allow" buttons, go through `AIAppearance.localizationProvider`. See [Customizing the appearance](https://getstream.io/chat/docs/sdk/ios/guides/ai-integrations/#customizing-the-appearance). --- For the most recent version of this documentation, visit [https://getstream.io/chat/docs/sdk/ios/guides/ai-integrations/reasoning-and-tool-calls/](https://getstream.io/chat/docs/sdk/ios/guides/ai-integrations/reasoning-and-tool-calls/).