Fix improper conversion of list[Audio | File | Image] helpers

[joshrubin-p360]

Description

Contributors Checklist

• My change closes Convert FastMCP Types to String if no ContentBlock in List Return Type #1969
• I have followed the repository's development workflow
• I have tested my changes manually and by adding relevant tests
• I have performed all required documentation updates

Review Checklist

• I have self-reviewed my changes
• My Pull Request is ready for review

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[strawgate]

this requires a more complex fix,

my guess is we might just need to change this:

    if any(isinstance(item, ContentBlock) for item in result):
        return [
            _convert_to_single_content_block(item, serializer)
            if not isinstance(item, ContentBlock)
            else item
            for item in result
        ]

to check for ContentBlock | Audio | Image | File in the any() clause

[joshrubin-p360]

this requires a more complex fix,

my guess is we might just need to change this:

    if any(isinstance(item, ContentBlock) for item in result):
        return [
            _convert_to_single_content_block(item, serializer)
            if not isinstance(item, ContentBlock)
            else item
            for item in result
        ]

to check for ContentBlock | Audio | Image | File in the any() clause

Yeah I saw the issue with my first fix, so I changed to only convert fastmcp types (Audio, Image, File).

May need to update some tests, I'm not sure if the failing tests is intended behavior or not.

[strawgate]

you will need to review the developer guide to ensure your change passes linting, formatting, and type checking and then I would recommend running the tests locally

I dont think you need to modify the isinstance check in the list comprehension

[strawgate]

I am happy to take over this PR if you'd like otherwise i'll leave you to it, please tag me when you're ready for a review or if you need any help

[joshrubin-p360]

I am happy to take over this PR if you'd like otherwise i'll leave you to it, please tag me when you're ready for a review or if you need any help

That’d be really helpful if you took over. I don’t currently have the bandwidth to finish up the PR so that’d be really helpful, thanks!

[strawgate]

@joshrubin-p360 should be ready for you to test

[Copilot]

Pull Request Overview

This PR fixes a bug in the fastmcp type conversion logic to correctly handle lists containing Image, Audio, and File types. The issue was that the condition checking for ContentBlock types was not comprehensive enough, causing mixed content lists to be incorrectly aggregated into a single TextContent block instead of being processed as individual content blocks.

• Updated the type checking condition to include Image, Audio, and File types alongside ContentBlock
• Added test coverage to verify the fix works correctly for lists of convertible types

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/fastmcp/tools/tool.py	Fixed the type checking condition in _convert_to_content to properly handle Image, Audio, and File types
tests/tools/test_tool.py	Added test case to verify conversion behavior with lists of content types

[joshrubin-p360]

@strawgate Thanks for getting this wrapped up!

[strawgate]

Let me know if you have any other issues!