Automatic repair invalid JSON formatted MCP messages generated by LLM

Is your feature request related to a problem? Please describe.
MCP request is transported in JSON format, which is generated by LLM. However, for LLMs that are not clever enough, the strings it generated are not always valid JSON. For example, LLM may generate [1, 2, 3, 4,], or { "page_index": "0" } while "page_index" requires an integer.

Describe the solution you'd like
Community has provided solutions such as json_repair, try_parse. I wonder if it is considered right decision to integrate such ability into the MCP framework, or at least exposes an interface for users to do such things.

Describe alternatives you've considered
Provide an interface before parsing plaintext string into JSON structures

Start by locating the MCP message parsing path and the interface before plaintext is parsed into JSON; the issue names no files or tests. Review the proposed json_repair and try_parse approaches, then clarify whether the goal is framework-integrated repair or an extension point, with acceptance criteria for malformed values and trailing commas.