devutils-mcp-server

Instructions

Implementation Reference

• src/tools/formatters.ts:42-94 (handler)

  The implementation of the json_validate tool, which validates JSON strings and returns either a success message or an error with position and context.

  server.tool(
    "json_validate",
    "Validate a JSON string and report any parsing errors with their approximate location.",
    { input: z.string().describe("The JSON string to validate") },
    async ({ input }) => {
      try {
        JSON.parse(input);
        return {
          content: [
            {
              type: "text" as const,
              text: JSON.stringify(
                { valid: true, message: "Valid JSON" },
                null,
                2
              ),
            },
          ],
        };
      } catch (e) {
        const message = e instanceof Error ? e.message : String(e);
  
        // Try to extract position info from error
        const posMatch = message.match(/position\s+(\d+)/i);
        const position = posMatch ? parseInt(posMatch[1], 10) : undefined;
  
        let context: string | undefined;
        if (position !== undefined) {
          const start = Math.max(0, position - 20);
          const end = Math.min(input.length, position + 20);
          context = input.slice(start, end);
        }
  
        return {
          content: [
            {
              type: "text" as const,
              text: JSON.stringify(
                {
                  valid: false,
                  error: message,
                  position,
                  context,
                },
                null,
                2
              ),
            },
          ],
        };
      }
    }
  );