💡 Feature Request: JSON → XML Compression for MCP Schema (47% Prompt Reduction)

[shariqriazz]

Hey team,

I’ve implemented a compression utility that converts verbose JSON-based MCP schemas into a compact XML format — reducing system prompt footprint significantly while preserving all tool functionality.

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🔍 Problem

MCP tools currently define schemas in JSON, which:

• Takes up a lot of space in the system prompt
• Adds to context bloat, especially when multiple tools are used
• Limits room for actual task-relevant instructions or dialogue

In a real-world case, a single MCP tool schema used 1,718 words — and that’s just the structure.

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✅ What I’ve done

I built a utility that:

• Converts JSON-based tool schemas into a compressed XML format
• Achieves ~47% context size reduction (1,718 → 904 words)
• Preserves:
  • All parameter metadata
  • Tool logic
  • Descriptions and options
• Outputs are deterministic and compatible with existing MCP tooling

No changes are needed to existing tools — just swap the JSON blob with the XML one in the prompt.

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🧪 Details

• Schema structure is fully retained — just compacted
• Includes a fallback mechanism to retain compatibility if needed
• Comes with a full test suite to ensure fidelity of conversion
• Works transparently: no effect on tool invocation or parsing

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📉 Results

Schema Format	Token Size
JSON	1,718 words
XML	904 words
Reduction	~47%

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Let me know if you're interested and I can PR the utility or share integration steps.

This change helps make MCP-based prompts much more efficient while remaining 100% compatible with the current tool engine.

[hassoncs]

This sounds super interesting / useful! I feel like we could easily put this behavior behind a new Experimental feature flag so folks try try it out

[xyOz-dev]

I second this, also for newer SOTA models like sonnet and opus they follow xml much more accurately therefore both being cheaper and more accurate is a massive improvement. -- good job.