Make older functions compatible with tool calling

[dirkbrnd]

Description

Some older custom function implementations where the description and parameters were manually specified (e.g. as built in composio-phidata) were not compatible with the new way of building tools for models.

This addresses it by keeping parameters/description if it was set on the Function.

Type of change

Please check the options that are relevant:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Model update
• Infrastructure change

Checklist

• My code follows Phidata's style guidelines and best practices
• I have performed a self-review of my code
• I have added docstrings and comments for complex logic
• My changes generate no new warnings or errors
• I have added cookbook examples for my new addition (if needed)
• I have updated requirements.txt/pyproject.toml (if needed)
• I have verified my changes in a clean environment

Additional Notes

Include any deployment notes, performance implications, or other relevant information: