MCP Server Access for Claude (forbidden)

[David Pérez Toscano]

Hi, 

I'm trying to connect the Amplify MCP Server to Claude Desktop on Windows. The Amplify API token works correctly (tested via curl against api.outbrain.com). 

However, when connecting to amplifymcp.outbrain.com I get 403 Forbidden. I used the official amplify-mcp-installer and it passed the connection test in SSE format, but Claude Desktop still shows Server disconnected. 

Do I need additional activation for the MCP Server beyond standard API access?  

Thanks!

[Danielle Newman]

Hello David,

Thanks for reaching out. 

Can you please confirm if the email you are using to connect to the API is the same as the email you are using to reach out? Looking at this account it hasn't been granted API access, so you will need to request it via https://www.outbrain.com/partner-api/ if this is the case.

If you are using a different email address, please provide it so I can look into this further. 

Kind regards,

Danielle

On Mon, 16 Mar 2026 at 10:46, David Pérez Toscano <pert...@gmail.com> wrote:

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[David Pérez Toscano]

Hi Danielle,

Sorry, the email is daltondi...@gmail.com

Thanks!

[Danielle Newman]

Hi David,

No problem. I've looked into this account and it seems to be set up correctly.

Would you be able to provide the trace id for the request producing the 403 error so we can investigate why it's occurring?

Kind regards,

Danielle

To view this discussion visit https://groups.google.com/d/msgid/outbrain-amplifyapi/0d50de05-9d37-4c1f-a1d0-2dd0fa8e34edn%40googlegroups.com.

[David Pérez Toscano]

Hi Danielle,
Thank you for looking into this. Here is the trace ID from the 403 request:
x-traceid: 7597a4979df33a2241624e386a1a45e1
Please let me know if you need anything else.
Best regards,
David

[Danielle Newman]

Hi David,

As we cannot find your trace id in our database, this indicates that the wrong MCP URL is being used. Please ensure you connect using the following URL - https://amplifymcp.outbrain.com/AmplifyMcp/mcp. If this doesn't help, can you please share the contents of your claude_desktop_config.json file so we can confirm if that's set up correctly.

Best regards,

Danielle

To view this discussion visit https://groups.google.com/d/msgid/outbrain-amplifyapi/2692ede6-4081-4aa6-9c31-02c9ba30f03an%40googlegroups.com.

[David Pérez Toscano]

Hi Danielle,

Here is my claude_desktop_config.json (token redacted):

json

{ "mcpServers": { "amplify-mcp-server": { "command": "npx", "args": [ "-y", "mcp-remote", "https://amplifymcp.outbrain.com/AmplifyMcp/mcp", "--header", "OB-TOKEN-V1:${AUTH_TOKEN}", "--transport", "sse" ], "env": { "AUTH_TOKEN": "***" } } } }

For reference, the Amplify API token works correctly when calling api.outbrain.com directly via curl. The 403 only occurs when connecting to amplifymcp.outbrain.com.

Best regards, 

David

[Danielle Newman]

Hi David,

Please use the following template found here replacing only "YOUR_API_TOKEN". 

{

  "mcpServers": {
    "amplify-mcp-server": {
      "command": "npx",
      "args": [
        "-y",
        "mcp-remote",

        "https://amplifymcp.outbrain.com/AmplifyMcp/mcp/",
        "--header",
        "Authorization:${AUTH_TOKEN}"
      ],
      "env": {
        "AUTH_TOKEN": "Bearer YOUR_API_TOKEN"
      }
    }
  }

} 

And please let us know if the issue persists. 

Kind regards,

Danielle

To view this discussion visit https://groups.google.com/d/msgid/outbrain-amplifyapi/5d47674b-ec82-4fe5-b6d9-7b57f497bd15n%40googlegroups.com.

[David Pérez Toscano]

Hi Danielle,

Good news — the connection is now working and all 37 tools load correctly. However, when calling any tool (e.g. get-my-amplify-marketers) the server returns a 504 Gateway Timeout. The SSE stream disconnects before the tool execution completes.

From the logs:

Error: SSE stream disconnected: TypeError: terminated StreamableHTTPError: 504 Gateway Time-out - The server didn't respond in time.

Is there a known issue with the MCP server response times?

Best regards, 

David

[Danielle Newman]

Hi David,

I'm happy to hear that the 403 error is now resolved!

Thanks for providing the log message for the 504 error. We've reached out to the developer team for this service and they are now looking into resolving this. We'll let you know when we hear back from them.

Best regards,

Danielle

To view this discussion visit https://groups.google.com/d/msgid/outbrain-amplifyapi/4305093a-9041-4217-9b4b-3fe5de1eb9b8n%40googlegroups.com.

[David Pérez Toscano]

Hi Danielle, any update on this? Thanks!

[Danielle Newman]

Hi David,

Sorry about the slow reply, I've just heard back from the developers regarding this, they made some improvements that should resolve this issue.

Please let us know if the issue persists, and I will inform them.

Best regards,

Danielle

To view this discussion visit https://groups.google.com/d/msgid/outbrain-amplifyapi/bb946048-510a-4cfe-b5fe-bebd0d599c3an%40googlegroups.com.