Test of custom connector returns 415, swagger editor fails

(1) Share

Report

Posted on by GO-20061201-0

Architecture:

An Azure app service is running an MCP server. That MCP server has an echo endpoint. That echo endpoint accepts POST and OPTIONS. I created a custom connector + connection.

Tests:

If I test the custom connector in Power Apps (page 6), it works. I send: echo "joe", it replies "hello joe". I check app insights and I see POST /echo and a 200.

If I test the connection using the swagger editor, it seems to fail in that UI - it reports:

Failed to fetch.
Possible Reasons:

CORS
Network Failure
URL scheme must be "http" or "https" for CORS request.

However, if I look in app insights, I see OPTIONS /echo (returns a 200) and POST /echo (also returns a 200).

I added CORS related code to get this outcome:

// Echo API endpoint for OPTIONS
app.MapMethods("/echo", new[] { "OPTIONS" }, (HttpContext httpContext) =>
{
    httpContext.Response.Headers["Access-Control-Allow-Methods"] = "POST, OPTIONS, GET";
    httpContext.Response.Headers["Access-Control-Allow-Headers"] = "Content-Type, Accept, x-api-key";
    httpContext.Response.Headers["Access-Control-Allow-Origin"] = "*";
    return Results.Ok();
});

I added the custom connector as a Tool in an agent. I issue the request "echo joe". In the instructions I told the agent to wrap double quotes around the input string (in this case "joe").

On the Activity page, the Connector Action bubbles on the left show a red circle with ! in it. The larger panel on the right shows:

connectorRequestFailureThe connector 'Echo test api' returned an HTTP error with code 415.

And indeed, if I look in app insights, I see POST /echo with a 415 return code.

Question 1: is there a way I can see the details of the interaction between the agent and the custom connector?

Question 2: why the variability in the various test contexts?

Question 3: got a suggestion? what can I do to fix it?

All responses (5)

Answers (0)

Romain The Low-Code... 356 on at

Like (0)

Report

Test of custom connector returns 415, swagger editor fails

@GO-20061201-0 thanks for the update, it's much appreciated since this part is not at the moment well documented :) since last post we (with my team) had different problem with integration of custom connector but none of them near your :( hope you will find and share answer ! (or some one could save you)
Suggested answer

GO-20061201-0 on at

Like (0)

Report

Test of custom connector returns 415, swagger editor fails

For the CORS message, it was necessary to add:

Access-Control-Allow-Origin = "*"

to the POST /echo response. I found the needed debugging information by using browser tools. And referenced this SO:

javascript - How do CORS and Access-Control-Allow-Headers work? - Stack Overflow

This answers question 1 - at least for testing the custom connector. And apparently, question 2 as well. The swagger editor sends the OPTIONS request, however, the test from the agent chat does not. So - still need to resolve the 415 question.

So - part of question 3 yet to be solved.
GO-20061201-0 on at

Like (0)

Report

Test of custom connector returns 415, swagger editor fails

> Unfortunately, Power Platform doesn’t currently expose full request/response payloads from agent-to-connector interactions in the UI.

Thanks. I was hoping there was a capability similar to in Azure AI Foundry that I just couldn't find. :/

> since you’re already logging requests, you can inspect the POST /echo entries use Application Insights.

I think I've already learned as much as I can from app insights

> SSE MCP is now considered obsolete for PP and Copilot studio

I knew that - the MCP server is http/streaming.
Romain The Low-Code... 356 on at

Like (0)

Report

Test of custom connector returns 415, swagger editor fails

previous answer is perfect, just to add : SSE MCP is now considered obsolet for PP and Copilot studio, try Streamable :) doc have change yesterday on MS learn :)
Suggested answer

Vahid Ghafarpour 167 on at

Like (1)

Report

Test of custom connector returns 415, swagger editor fails

Unfortunately, Power Platform doesn’t currently expose full request/response payloads from agent-to-connector interactions in the UI. However,
since you’re already logging requests, you can inspect the POST /echo entries use Application Insights.