MCP Evaluation: Surprising Results in Cursor

In Claude Code with claude-sonnet-4, I got the following response.

> /model
  ⎿  Set model to sonnet (claude-sonnet-4-20250514)

> What are the top 5 errors in my application? Use the Observe MCP server to answer the question.

⏺ I'll use the Observe MCP server to find the top 5 errors in your application.

⏺ observe - generate-query-card (MCP)(prompt: "What are the top 5 errors in my application?")
  ⎿  Top 5 Errors in Application
  ⎿  # Time Range
     8/22/2025, 4:41:15 PM to 8/22/2025, 8:41:15 PM
  ⎿  # Inputs
     - tracing_service_metrics: 42496705
  ⎿ filter (metric = "apm_service_error_count_with_status")
    statsby total_error_count:sum(value), group_by(status_code:tags."status.code", service_name:tags."service.name", operation:tags."span.name",
     status_message:tags."status.message")
    … +1 line (ctrl+r to expand)

  ⎿ # Observe link to this query
            This should be included in the response and analysis returned to the user
            IMPORTANT: Never modify the url string- use it exactly as is <url>https://146268791759.observeinc.com/workspace/41249703/worksheet/f
    … +1 line (ctrl+r to expand)

  ⎿  # Query Results

     Time Range: 8/22/2025, 4:41:15 PM to 8/22/2025, 8:41:15 PM
     … +9 lines (ctrl+r to expand)

⏺ Based on the query results from your Observe platform, here are the top 5 errors in your application:

  1. Frontend POST Error (500) - 1,654 errors
    - Service: frontend
    - Status: 500 Internal Server Error
  2. Checkout Payment Failure (gRPC 13) - 1,654 errors
    - Service: checkout
    - Operation: CheckoutService/PlaceOrder
    - Message: Payment card charge failed with invalid token error
  3. Payment Service Error - 1,654 errors
    - Service: payment
    - Operation: PaymentService/Charge
    - Related to the checkout payment failures
  4. Frontend Checkout API Error (500) - 0 recent errors
    - Service: frontend
    - Endpoint: POST /api/checkout
  5. Frontend Redirect (308) - 0 recent errors
    - Service: frontend
    - Operation: GET request

  The main issue appears to be a payment processing failure causing cascading errors across your frontend and checkout services.

  https://146268791759.observeinc.com/workspace/41249703/worksheet/f3hj7nwi~?s=44328-318uwhud