[Jae Birdsall (jaeminbird)]

Motivation and Context

MCP sends image/audio data and blob blob as base64, but the MCP connector builds ImageContent/AudioContent/BinaryContent without data_format="base64". So .data holds the base64 text, data_uri becomes data:image/png;,iVBOR... (no ;base64), and blob resources lose their mimeType (text/plain). Tool results, prompts and sampling messages with images reach the model broken; the Google AI connector sends the base64 text as image bytes.

Description

Pass data_format="base64" for the three types, and the resource mimeType for blobs.

• New test covers image, audio and a blob resource via call_tool and get_prompt; fails before, passes after.
• urllib.request.urlopen(content.data_uri) now returns the original bytes (before: the base64 text).
• tests/unit/connectors/mcp and tests/unit/contents pass; ruff and mypy clean.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the SK Contribution Guidelines and the pre-submission formatting script raises no violations
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄

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[Jae Birdsall (jaeminbird)]

@microsoft-github-policy-service agree

[Eduard van Valkenburg (eavanvalkenburg)]

This is approved, but GitHub now marks its merge-queue entry UNMERGEABLE. I confirmed a conflict with #14676 in python/tests/unit/connectors/mcp/test_mcp.py: both PRs append tests at the same location. Please rebase after #14676 lands and keep both sets of regression tests.

[Jae Birdsall (jaeminbird)]

Rebased onto main after #14676 (a68f006). Both sets of tests are kept in test_mcp.py, and tests/unit/connectors/mcp passes (69 tests).

[Jae Birdsall (jaeminbird)]

Rebased again onto current main (4c8d27c), which also picks up #14095 in mcp.py. Both sets of regression tests from #14676 and this PR are kept in test_mcp.py; tests/unit/connectors/mcp passes (73 tests) and ruff/mypy are clean. Thanks Eduard van Valkenburg (@eavanvalkenburg) for tracking down the conflict.