fix: downgrade MCP "Unexpected content type" log spam from ERROR to DEBUG

[opspawn]

Summary

Fixes #1200

The observability-agent logs mcp.client.streamable_http - ERROR - Unexpected content type: every 30 seconds when connected to the kagent-tools MCP server. This happens because the Go mcp-go library returns 200 OK without a Content-Type header for heartbeat ping-responses, and the Python MCP SDK treats any unexpected Content-Type as an error.

These errors are benign -- actual MCP tool calls work correctly -- but they spam the logs and obscure real problems.

Changes

• python/packages/kagent-adk/src/kagent/adk/_logging.py (new): Logging filter that downgrades "Unexpected content type" ERROR records from mcp.client.streamable_http to DEBUG level. The messages remain visible when DEBUG logging is enabled.
• python/packages/kagent-adk/src/kagent/adk/__init__.py: Installs the filter at import time so it takes effect for all kagent agents automatically.
• python/packages/kagent-adk/tests/unittests/test_logging_filter.py (new): 8 unit tests covering filter behavior, idempotent installation, and end-to-end integration.

Root cause note

The upstream root cause is in kagent-dev/tools (and transitively in mark3labs/mcp-go), where the isPingResponse handler in StreamableHTTPServer.handlePost does a bare return without setting Content-Type: application/json on the response. A complementary fix there would fully resolve the issue at the source. This PR addresses the symptom on the Python client side within this repo.

Test plan

• All 8 new unit tests pass
• All existing kagent-adk unit tests pass (82/82; 9 pre-existing TLS e2e failures unrelated)
• ruff check passes on all changed files
• Deploy with observability-agent enabled and verify the log spam is eliminated

[Copilot]

Pull request overview

This PR addresses noisy log spam from the MCP Python SDK client by implementing a logging filter that downgrades "Unexpected content type" ERROR messages to DEBUG level. The issue occurs because the Go-based kagent-tools MCP server doesn't set a Content-Type header on heartbeat ping responses, causing the Python MCP client to log errors every 30 seconds. While these errors are benign (actual tool calls work correctly), they obscure real problems in the logs.

Changes:

• Adds a new _logging.py module with a filter that downgrades specific MCP client ERROR messages to DEBUG level
• Installs the filter automatically at package import time in __init__.py
• Provides comprehensive unit tests (8 tests) covering filter behavior, idempotency, and end-to-end integration

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
python/packages/kagent-adk/src/kagent/adk/_logging.py	New module implementing the _UnexpectedContentTypeFilter that downgrades "Unexpected content type" ERROR logs to DEBUG, plus an idempotent installation function
python/packages/kagent-adk/src/kagent/adk/__init__.py	Imports and installs the filter at module initialization time so it's active for all kagent agents
python/packages/kagent-adk/tests/unittests/test_logging_filter.py	New comprehensive test suite covering filter behavior, edge cases, idempotency, and end-to-end integration

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

The logging module is imported but never used in this file. Since install_mcp_content_type_filter() doesn't require the logging module to be imported in the calling code, this import can be removed.

Suggested change

import logging