Test scope: 75 read tools exercised against a production Meta Business estate. The tools below failed with errors that point at the MCP server itself rather than at permissions or missing config. They split into six categories ordered roughly by remediation cost and business impact.
This is the most damaging category because it knocks out the entire performance-reporting surface. The same root cause shows up at all four levels of the ads hierarchy plus across Page and Post insights.
meta_get_account_insights, meta_get_campaign_insights, meta_get_adset_insights, and meta_get_ad_insights all return (#100) unique_impressions is not valid for fields param. please check https://developers.facebook.com/docs/marketing-api/reference/ads-insights/ for all valid values. Meta retired the unique_impressions field in the Marketing API some time ago — it now lives behind the reach field instead. The MC