Avoiding to parse string arguments containing valid JSON if the argument annotation is str

[cjg]

Every time a parameter of a tool is passed as a string containing a valid JSON it is parsed and replaced. From the comment of pre_parse_json() "This is to handle cases like ["a", "b", "c"] being passed in as JSON inside a string rather than an actual list"

Nevertheless this method doesn't check if the annotation of parameters indicates that it is supposed to be a str rather than a dict or a list

Types of changes

• 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 change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

[bhosmer-ant]

@cjg thank you for this!