Add Microsoft Advertising (Bing Ads) third-party MCP plugin

[SamSokolin]

Summary

Adds third_party/microsoft-ads, a marketplace plugin for Microsoft's official hosted Microsoft Advertising MCP server, mirroring the structure of third_party/x-ads.

• Endpoint (from Microsoft's MCP Server Setup Guide): https://partner.api.bingads.microsoft.com/ext/mcp/vnext?toolSetNames=OpenBeta — the same URL Microsoft documents for VS Code and Claude.
• Auth: Microsoft Entra ID OAuth. Microsoft does not publish a shared OAuth client, so the plugin declares a CLIENT_ID plugin variable (the user's own Entra app registration) and authenticates as a public client with PKCE. Scopes: https://ads.microsoft.com/msads.manage, offline_access. No client secret and no invented credentials.
• README documents app registration (public-client platform, Cursor's two redirect URIs, msads.manage delegated permission), plugin configuration, the read-only open-beta tool set (GetAccounts, GetCampaigns, GetAdGroups, GetAds, GetKeywords, GetAssetGroups, GetAudienceAssociations), and troubleshooting.
• Logo: Microsoft's four-square symbol on a white tile with padding, consistent with the Outlook/OneDrive plugins.
• Registered in .cursor-plugin/marketplace.json and the root README.md table.

Files

third_party/microsoft-ads/
├── .cursor-plugin/plugin.json
├── assets/logo.svg
├── mcp.json
├── README.md
├── CHANGELOG.md
└── LICENSE

Verification

• node scripts/validate-plugins.mjs → All plugins validated successfully.
• mcp.json / plugin.json parse as JSON; logo.svg renders correctly at 192×192.

Notes for reviewers

• The about.ads.microsoft.com landing page links to the Learn setup guide; the guide is the source for the URL, auth endpoints, and scopes.
• Official sources: overview, setup guide, tools, use cases.