Insted of sending tool result content in string format use structuredContent and outputSchema.

[jeet-at]

Specification link : https://modelcontextprotocol.io/specification/draft/server/tools#output-schema

Tools may also provide an output schema for validation of structured results. If an output schema is provided.

Example tool with output schema:
{ "name": "get_weather_data", "description": "Get current weather data for a location", "inputSchema": { "type": "object", "properties": { "location": { "type": "string", "description": "City name or zip code" } }, "required": ["location"] }, "outputSchema": { "type": "object", "properties": { "temperature": { "type": "number", "description": "Temperature in celsius" }, "conditions": { "type": "string", "description": "Weather conditions description" }, "humidity": { "type": "number", "description": "Humidity percentage" } }, "required": ["temperature", "conditions", "humidity"] } }

Example valid response for this tool:

{ "jsonrpc": "2.0", "id": 5, "result": { "content": [ { "type": "text", "text": "{\"temperature\": 22.5, \"conditions\": \"Partly cloudy\", \"humidity\": 65}" } ], "structuredContent": { "temperature": 22.5, "conditions": "Partly cloudy", "humidity": 65 } } }