> ## Documentation Index > Fetch the complete documentation index at: https://docs.apostra.com/llms.txt > Use this file to discover all available pages before exploring further. # Channel groups > Express composite inventory intent, compile it into media buys, and preserve the same grouping in reporting A **channel group** is one coherent inventory selection inside a campaign. It combines AdCP inventory dimensions without inventing new AdCP channel values. For example, mobile web display means: ```json theme={null} { "channels": ["display"], "propertyTypes": ["website"], "deviceTypes": ["mobile"] } ``` It does not mean `channel: "mobile_web"`. `mobile_web` is not an AdCP media channel. Interchange uses the channel-group ID to split and label media buys. It does not currently filter discovery, validate selected products against the group's inventory definition, or translate that definition into package targeting. Murph and API clients must verify discovery evidence and seller product details before assigning `channelGroupId`. Within one inventory dimension, values are alternatives (OR). Across populated dimensions, declared values combine (AND). A group with `channels: ["ctv", "olv"]` and `deviceTypes: ["ctv", "mobile"]` therefore allows either channel and either device, while still declaring both a listed channel and a listed device. If you need pairwise logic such as “CTV on CTV devices OR OLV on mobile devices”, make two channel groups. ## Why groups create media-buy boundaries One downstream AdCP media buy cannot preserve arbitrary Boolean combinations across channel, property type, device type, and format. Interchange therefore uses this compilation rule: ```text theme={null} channel group × seller × settlement currency = one media buy ``` If a campaign contains `mobile-web-display` and `ctv`, products assigned to those groups become separate media buys even when they use the same seller and currency. They remain part of one campaign. ## Save pre-built groups Pass `channelGroups` to `save_campaign` on `/mcp/v3`. A preset is authoring shorthand. Interchange expands and saves the full definition with the preset version, so later preset changes do not silently change an existing campaign. ```json theme={null} { "advertiserId": "123", "name": "Streaming launch", "flight": { "startAt": "2027-02-01T00:00:00Z", "endAt": "2027-02-28T23:59:59Z" }, "budget": { "total": 50000, "currency": "USD" }, "channelGroups": [ { "channelGroupId": "mobile-web-display", "presetId": "mobile_web_display" }, { "channelGroupId": "ctv", "presetId": "ctv" } ], "idempotencyKey": "streaming-launch-2027-02" } ``` The available presets expand as follows: | Preset | Saved inventory definition | | -------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `display` | `channels: ["display"]` | | `olv` | `channels: ["olv"]` | | `ctv` | `channels: ["ctv"]` | | `mobile_web_display` | `channels: ["display"]`, `propertyTypes: ["website"]`, `deviceTypes: ["mobile"]`, and AdCP display `formatKinds` (`image`, `html5`, `display_tag`, `image_carousel`, `native_in_feed`, `sponsored_placement`, `responsive_creative`, `custom`) | | `mobile_web_olv` | `channels: ["olv"]`, `propertyTypes: ["website"]`, `deviceTypes: ["mobile"]` | The simple channel presets deliberately make no property, device, or format assumption. For example, `ctv` means the AdCP CTV channel; it does not silently mean only a physical television device or only a CTV app. ## Define your own group You can provide the same AdCP-aligned dimensions directly: ```json theme={null} { "channelGroupId": "premium-streaming-video", "name": "Premium streaming video", "inventory": { "channels": ["ctv", "olv"], "propertyTypes": ["ctv_app", "website"], "deviceTypes": ["ctv", "desktop"], "formatKinds": ["video_hosted", "video_vast"] } } ``` Use separate groups when combinations must not collapse into a cross-product. Do not put an alias such as `mobile_web` into `channels`; aliases belong in the group name or preset ID, while the saved inventory definition stays aligned to AdCP. ## Assign products when creating a media buy Discover products, verify that the seller evidence matches one group, then pass that group's ID when creating the draft. With `save_media_buy`, `channelGroupId` applies to all products in that creation call: ```json theme={null} { "campaignId": "cmp_123", "sellerId": "42", "channelGroupId": "mobile-web-display", "products": [ { "productId": "sf1:42:bW9iaWxlLWRpc3BsYXk", "budget": 15000 } ], "idempotencyKey": "pq_123" } ``` When using the batch `create_media_buys` operation directly, put `channelGroupId` on each product or proposal selection. Every selection needs a group ID when its campaign defines channel groups. A media buy records the group ID and name that created it. Define groups before the campaign creates its first ungrouped media buy. Once a saved selection or media buy references a group, keep it immutable; add a new group instead of removing or redefining it. The batch operation also accepts fully expanded `channelGroups` in `campaign.create`. Preset shorthand is available through V3 `save_campaign`; REST clients either send the canonical saved shape inline or create the campaign first and pass its `campaignId`. REST does not accept preset shorthand. Send `name`, `source`, and the expanded inventory snapshot: ```json theme={null} { "channelGroups": [ { "channelGroupId": "mobile-web-display", "name": "Mobile web display", "source": { "kind": "preset", "presetId": "mobile_web_display", "presetVersion": 1 }, "inventory": { "channels": ["display"], "propertyTypes": ["website"], "deviceTypes": ["mobile"], "formatKinds": [ "image", "html5", "display_tag", "image_carousel", "native_in_feed", "sponsored_placement", "responsive_creative", "custom" ] } } ] } ``` Always pass product and proposal IDs exactly as discovery returned them. The qualified `sf1:` value in the example is illustrative; do not construct or decode it in a client. ## Report by the same group Use the V3 `get_delivery` tool with the `campaign_delivery` report and the `channel_group` dimension: ```json theme={null} { "report": "campaign_delivery", "metrics": ["impressions", "spend", "clicks"], "dimensions": ["channel_group"], "range": { "startDate": "2026-09-01", "endDate": "2026-09-30" }, "filters": { "campaignId": "cmp_123" } } ``` To read one group only, add `filters.channelGroupId`. Ungrouped legacy media buys roll up under a null channel group rather than being guessed from their names, products, or delivery. Channel groups answer “which coherent inventory selection did the buyer ask for?” Campaign targeting answers “who, where, or when should it reach?” Keep those concepts separate even when both mention a dimension such as device.