meta-ads MCP OAuth fails: "redirect_uris are not registered for this client"

Summary

The meta-ads MCP server (https://mcp.facebook.com/ads, shipped as mcp__meta-ads__*) cannot complete OAuth authentication. The auth flow fails before returning an authorization URL — the OAuth client itself is rejected by Meta during validation.

Error

Failed to start OAuth flow for meta-ads: SDK auth failed: The provided redirect_uris are not registered for this client.

Reproduction

1. In Claude Code, invoke mcp__meta-ads__authenticate (or run /mcp and try to authenticate to meta-ads).
2. The call returns the error above instead of an authorization URL.
3. The tool's own fallback suggestion (Ask the user to run /mcp and authenticate manually.) does not help — the /mcp dialog dismisses without progressing because the failure is upstream of the user-facing browser step.

Expected

A facebook.com authorization URL is returned that the user can open in a browser to complete OAuth.

Actual

Auth flow never starts; no URL is ever generated. Failure occurs during OAuth client registration/validation at Meta.

Environment

• Claude Code: 2.1.143
• OS: macOS 26.5 (build 25F71)
• MCP server: meta-ads (HTTP, https://mcp.facebook.com/ads)
• Other Claude-hosted MCPs (e.g. claude_ai_Google_Drive) are unaffected on the same install.

Suspected cause

The redirect_uri Claude Code presents during OAuth client registration is not on Meta's allowlist for this OAuth app. Likely needs a server-side fix: either register the Claude Code redirect URI with Meta's OAuth app, or update the meta-ads MCP integration to use an already-registered redirect URI.

Contact

contact@siddharth-dev.tech