update_meta_placements

Set the channel-level Meta placement default of an existing DRAFT wizard campaign's Facebook or Instagram channel: automatic placements (Meta decides where ads serve) or a manual list of surfaces (Feed, Stories, Reels, ...).

                Placements are where the ads serve inside Meta's networks. This is the same
                "Placements" control the platform UI shows in the Facebook/Instagram section of
                the campaign draft page. The campaign MUST already have the channel enabled
                (via create_campaign / add_and_edit_campaign_elements).

                ⚠️ DRAFT-ONLY: the platform rejects the edit once the campaign is Launching/Launched.

                KEYWORDS: meta, facebook, instagram, threads, placements, placement, feed, stories,
                reels, explore, search results, profile feed, automatic placements, manual placements,
                advantage+ placements, where ads serve, surfaces, channel settings, campaign settings

                WHEN TO USE:
                - Serve ads only on specific surfaces (e.g. Instagram Reels and Stories)
                - Switch a channel back to automatic placements (Meta optimizes delivery)
                - The user asks where their Facebook/Instagram ads will appear

                PARAMETERS:
                - campaign_id: the wizard campaign ID (required)
                - channel: FACEBOOK | INSTAGRAM (required — the campaign channel to edit)
                - mode: AUTO | MANUAL (required). AUTO = automatic placements, clears any
                  manual set. MANUAL = serve only on the placements listed.
                - placements: array of placement codes, required when mode=MANUAL, ignored
                  for AUTO. Facebook surfaces: FB_FEED, FB_STORIES, FB_REELS,
                  FB_SEARCH_RESULTS. Instagram surfaces: IG_FEED, IG_PROFILE_FEED,
                  IG_EXPLORE, IG_EXPLORE_HOME, IG_STORIES, IG_REELS, IG_SEARCH_RESULTS.
                  Threads: TH_THREADS_STREAM.

                PLACEMENT RULES (enforced; violations return a descriptive error):
                - Companion rules: FB_STORIES and FB_SEARCH_RESULTS require FB_FEED;
                  IG_PROFILE_FEED, IG_SEARCH_RESULTS and IG_EXPLORE require IG_FEED;
                  IG_EXPLORE_HOME requires IG_EXPLORE; TH_THREADS_STREAM requires IG_FEED.
                - An INSTAGRAM channel accepts IG_* placements only.
                - A FACEBOOK channel always accepts FB_* placements. IG_* / TH_* placements
                  on a FACEBOOK channel additionally need the account's unified-placement
                  rollout (feature flag CORE_META_IG_PLACEMENT_ON_FB) — the platform rejects
                  them on accounts without it.
                - IG_PROFILE_FEED is not available on Lead Gen (CPL) campaigns.
                - AUTO is rejected while the channel has ad groups (per-ad-group setups keep
                  manual placements).

                This tool sets the campaign-wide default for the channel. Per-ad-group
                placement overrides exist in the platform UI but are not editable through
                chat yet — send users to the campaign page for per-ad-group customization.

                EXAMPLES:

                Instagram channel, Reels + Stories + Feed only:
                update_meta_placements({"campaign_id": 12345, "channel": "INSTAGRAM",
                    "mode": "MANUAL", "placements": ["IG_FEED", "IG_STORIES", "IG_REELS"]})

                Facebook channel back to automatic placements:
                update_meta_placements({"campaign_id": 12345, "channel": "FACEBOOK", "mode": "AUTO"})

                RESPONSE: {success, campaign_id, channel_id, channel, campaign_status,
                applied:{mode, placements}, previous?, errors?}
                `previous` echoes the channel's placement state before the edit.

                INTEGRATION WITH OTHER TOOLS:
                - Use search_campaigns_by_names / get_campaign_by_wizard_id to find the campaign
                - The channel is enabled by create_campaign or add_and_edit_campaign_elements
                - Reddit placements (feed/conversations) are a different system: use
                  update_reddit_channel_settings for those